diff --git a/API.md b/API.md
index bce791c..a00f2e3 100644
--- a/API.md
+++ b/API.md
@@ -14,6 +14,9 @@ For shapes, the following functions are available:
 - `noordstar_caves.unregister_shape(name)` Remove a defined cave shape
 - `noordstar_caves.clear_registered_shapes()` Remove all known cave shapes
 
+Generally, it is recommended to keep the number of cave shapes below 100.
+A good number of shapes is 10 for diversity but performance.
+
 The shapes are defined as follows:
 
 ```lua
@@ -132,12 +135,6 @@ The biomes are defined as follows:
     -- Keep in mind that cave biomes can blend, so it might not always look
     -- very smooth.
 
-    node_shell = "foo:permafrost",
-    depth_shell = 3,
-    -- Node forming a layer around the entire cave and thickness of this layer
-    -- You can make the depth as high as you want, but raising it past 16
-    -- might cause hard cut-offs at chunk edges.
-
     y_max = -100,
     y_min = -31000,
     -- Upper and lower limits of the cave biome.
@@ -160,3 +157,121 @@ The biomes are defined as follows:
     -- but can exceed these values.
 }
 ```
+
+## Decorations
+
+As a final part of generating the caves, decorations can be added to add unique
+structures to cave biomes.
+
+For decorations, the following functions are defined:
+
+- `noordstar_caves.register_decoration(decoration def)` Define a new cave decoration
+- `noordstar_caves.clear_registered_decorations()` Remove all known cave decorations
+
+The decorations are defined as follows:
+
+```lua
+{
+    deco_type = "simple",
+    -- Type. "simple" or "schematic" supported
+
+    place_on = "floor",
+    -- Side of the cave to place the decoration on. "floor" or "ceiling" supported
+
+    fill_ratio = 0.02,
+    -- Percentage of surface nodes on which this decoration will spawn
+
+    biomes = { "noordstar_caves:tundra", "foo:desert" },
+    -- List of (cave!) biomes that this decoration will spawn in. Occurs in all
+    -- biomes if this is omitted.
+
+    y_min = -31000,
+    y_max =  31000,
+    -- Lower and upper limits for decoration (inclusive).
+    -- These parameters refer to the Y-coordinate of the node where it is
+    -- originally chosen to be placed.
+
+    ----- Simple-type parameters
+
+    decoration = "foo:grass",
+    -- The node name used as the decoration.
+    -- If instead a list of strings, a randomly selected node from the list
+    -- is placed as the decoration.
+
+    height = 1,
+    -- Decoration height in nodes.
+    -- If height_max is not 0, this is the lower limit of a randomly selected
+    -- height.
+    -- Height can not be over 16.
+
+    height_max = 0,
+    -- Upper limit of the randomly selected height.
+    -- If absent, the parameter `height` is used as a constant.
+    -- Max height will be capped at 16.
+
+    place_offset_y = 0,
+    -- Y offset of the decoration base node relative to the standard base node
+    -- position.
+    -- Can be positive or negative. Default is 0.
+
+    ----- Schematic-type parameters
+
+    schematic = "foobar.mts",
+    -- If schematic is a string, it is the filepath relative to the correct
+    -- working directory of the specified Minetest schematic file.
+    -- Could also be the ID of a previously registered schematic.
+
+    schematic = {
+        size = {x = 4, y = 6, z = 4},
+        data = {
+            {name = "default:cobble", param1 = 255, param2 = 0},
+            {name = "default:dirt_with_grass", param1 = 255, param2 = 0},
+            {name = "air", param1 = 255, param2 = 0},
+              ...
+        },
+        yslice_prob = {
+            {ypos = 2, prob = 128},
+            {ypos = 5, prob = 64},
+              ...
+        },
+    },
+    -- Alternative schematic specification by supplying a table. The fields
+    -- size and data are mandatory whereas yslice_prob is optional.
+    -- See 'schematic specifier' in the Minetest Lua API documentation.
+
+
+    replacements = {["oldname"] = "convert_to", ...},
+    -- Map of node names to replace in the schematic after reading it.
+
+    flags = "place_center_x, place_center_y, place_center_z",
+    -- Flags for schematic decorations. See 'Schematic attributes'.
+
+    rotation = "90",
+    -- Rotation can be "0", "90", "180", "270", or "random"
+
+    place_offset_y = 0,
+    -- If the flag 'place_center_y' is set this parameter is ignored.
+    -- Y offset of the schematic base node layer relative to the 'place_on'
+    -- node.
+    -- Can be positive or negative. Default is 0.
+    -- Effect is NOT inverted for decorations on the ceiling.
+    -- Ignored by 'y_min' and 'y_max' checks, which always refer to the
+    -- 'place_on' node.
+}
+```
+
+## Ores
+
+This mod does not support adding ores to the caves, as this is a feature that
+is already well-supported by the Minetest Lua API and doesn't need a mod like
+this.
+
+## Misc
+
+In case you wish to do a few other operations, here's a few other functions
+that might be helpful to you:
+
+- `noordstar_caves.set_world_height(h)` Set the world's height to a given number.
+
+This feature is currently only supported in VoxeLibre. Contributions that help
+change the world depth in other games, are very welcome.
diff --git a/init.lua b/init.lua
index e60370b..2314bf5 100644
--- a/init.lua
+++ b/init.lua
@@ -92,6 +92,9 @@ noordstar_caves =
     -- A public list of all registered biomes
     , registered_biomes = {}
 
+    -- A public list of all registered decorations
+    , registered_decorations = {}
+
     -- A public list of all registered shapes
     , registered_shapes = {}
 
@@ -102,6 +105,11 @@ function noordstar_caves.clear_registered_biomes()
     noordstar_caves.registered_biomes = {}
 end
 
+-- Remove all registered decorations and start with a clean slate
+function noordstar_caves.clear_registered_decoration()
+    noordstar_caves.registered_decorations = {}
+end
+
 -- Remove all registered shapes and start with a clean slate
 function noordstar_caves.clear_registered_shapes()
     noordstar_caves.registered_shapes = {}
@@ -116,6 +124,15 @@ function noordstar_caves.register_biome(def)
     end
 end
 
+-- Register a new cave decoration
+function noordstar_caves.register_decoration(def)
+    local d = internal.clean_deco_def(def)
+
+    if d then
+        table.insert(noordstar_caves.registered_decorations, d)
+    end
+end
+
 -- Register a new cave shape
 function noordstar_caves.register_shape(def)
     local d = internal.clean_shape_def(def)
@@ -257,6 +274,64 @@ function internal.clean_biome_def(def)
     return d
 end
 
+-- Clean the user input on a decoration definition before inserting it.
+function internal.clean_deco_def(def)
+    if def.deco_type ~= "simple" and def.deco_type ~= "schematic" then
+        return nil
+    end
+    if def.deco_type == "simple" and type(def.decoration) ~= "string" then
+        return nil
+    end
+    if def.deco_type == "schematic" then
+        if type(def.schematic) == "string" then
+        elseif type(def.schematic) == "table" then
+        else
+            return nil
+        end
+    end
+    if type(def.fill_ratio) ~= "number" then
+        return nil
+    end
+
+    local d = {
+        deco_type = def.deco_type,
+        decoration = def.decoration,
+        schematic = def.schematic,
+        fill_ratio = def.fill_ratio,
+        biomes = def.biomes,
+    }
+
+    if def.place_on == "floor" or def.place_on == "ceiling" then
+        d.place_on = def.place_on
+    else
+        d.place_on = "floor"
+    end
+
+    local function place(key, t, default)
+        if type(def[key]) == t then
+            d[key] = def[key]
+        else
+            d[key] = default
+        end
+    end
+
+    place("y_min", "number", internal.world_minp.y)
+    place("y_max", "number", internal.world_maxp.y)
+    place("height_max", "number", 0)
+    place("height", "number", 1)
+    place("place_offset_y", "number", 0)
+    place("replacements", "table", {})
+    place("flags", "string", "place_center_x,place_center_z")
+    place("rotation", "string", "0")
+
+    d.height     = math.max(d.height    ,  0)
+    d.height     = math.min(d.height    , 16)
+    d.height_max = math.max(d.height_max,  0)
+    d.height_max = math.min(d.height_max, 16)
+
+    return d
+end
+
 -- Clean the user input on a shape definition before inserting it.
 function internal.clean_shape_def(def)
     if type(def.name) ~= "string" then
@@ -292,16 +367,18 @@ function internal.clean_shape_def(def)
 end
 
 -- Get the most nearby cave biome
-function internal.closest_cave_biome(heat, humidity)
+function internal.closest_cave_biome(heat, humidity, pos)
     local biome = internal.default_biome()
     local d = internal.biome_def_distance(biome, heat, humidity)
 
     for _, def in pairs(noordstar_caves.registered_biomes) do
-        local new_d = internal.biome_def_distance(def, heat, humidity)
-
-        if new_d <= d then
-            biome = def
-            d = new_d
+        if internal.is_valid_pos(pos, def.minp, def.maxp) then
+            local new_d = internal.biome_def_distance(def, heat, humidity)
+    
+            if new_d <= d then
+                biome = def
+                d = new_d
+            end
         end
     end
 
@@ -309,16 +386,18 @@ function internal.closest_cave_biome(heat, humidity)
 end
 
 -- Get the most nearby cave shape
-function internal.closest_cave_shape(cnct, vrtcl)
+function internal.closest_cave_shape(cnct, vrtcl, y)
     local shape = internal.default_shape()
     local d = internal.shape_def_distance(shape, cnct, vrtcl)
 
     for key, def in pairs(noordstar_caves.registered_shapes) do
-        local new_d = internal.shape_def_distance(def, cnct, vrtcl)
-
-        if new_d <= d then
-            shape = def
-            d = new_d
+        if def.y_min <= y and y <= def.y_max then
+            local new_d = internal.shape_def_distance(def, cnct, vrtcl)
+    
+            if new_d <= d then
+                shape = def
+                d = new_d
+            end
         end
     end
 
@@ -442,7 +521,7 @@ function internal.flat_from_cave_bools(minp, maxp)
             local cnct = connectivity:get_index(i)
             local vrtcl = verticality:get_index(i)
 
-            local def = internal.closest_cave_shape(cnct, vrtcl)
+            local def = internal.closest_cave_shape(cnct, vrtcl, pos.y)
             
             return def.name
     end)
@@ -496,6 +575,11 @@ function internal.flat_from_node_types(bools, minp, maxp)
                 return nt.floor_deco
             end
 
+            if bools:get_index(i + bools.up) == false then
+                -- Block is near the ceiling
+                return nt.ceiling_deco
+            end
+
             return nt.air
         else
             -- NOT PART OF CAVE
@@ -614,6 +698,8 @@ function internal.generate_caves(data, minp, maxp)
     -- Get cave bools
     local bools = internal.flat_from_cave_bools(bminp, bmaxp)
 
+    timer.checkpoint("Calculate cave shape")
+
     -- Get node types
     local nts = internal.flat_from_node_types(bools, bminp, bmaxp)
 
@@ -625,13 +711,16 @@ function internal.generate_caves(data, minp, maxp)
         internal.humidity_noise_params(), bminp, bmaxp
     )
 
+    timer.checkpoint("Calculate block types & biomes")
+
     local air = minetest.get_content_id("air")
+    local schems = {}
 
     -- Place blocks where necessary
     internal.iter_3d_area(bminp, bmaxp, function (i, pos)
         
+        local vi = vmanip:pos_to_index(pos)
         local function place(name)
-            local vi = vmanip:pos_to_index(pos)
 
             if vmanip:get_index(vi) == air then
             elseif type(name) == "string" then
@@ -648,14 +737,12 @@ function internal.generate_caves(data, minp, maxp)
         elseif nt == internal.node_types.stick_edge then
         elseif nt == internal.node_types.air then
             place("air")
-        elseif nt == internal.node_types.floor_deco then
-            -- TODO: Place registered decoration
         else
             -- Find appropriate biome
             local heat = heat_points:get_index(i)
             local humidity = humidity_points:get_index(i)
 
-            local def = internal.closest_cave_biome(heat, humidity)
+            local def = internal.closest_cave_biome(heat, humidity, pos)
 
             if nt == internal.node_types.floor then
                 place(def.node_floor)
@@ -663,6 +750,41 @@ function internal.generate_caves(data, minp, maxp)
                 place(def.node_wall)
             elseif nt == internal.node_types.ceiling then
                 place(def.node_roof)
+            elseif nt == internal.node_types.floor_deco or nt == internal.node_types.ceiling_deco then
+                local schem_placed = false
+                local appropriate_place = "floor"
+                if nt == internal.node_types.ceiling_deco then
+                    appropriate_place = "ceiling"
+                end
+
+                if not schem_placed then
+                    -- Prevent decorations from spawning in the air
+                    if vmanip:get_index(vi) == air then
+                        schem_placed = true
+                    end
+                end
+
+                if not schem_placed then
+                    for _, deco in ipairs(noordstar_caves.registered_decorations) do
+                        if deco.place_on ~= appropriate_place then
+                        elseif math.random() > deco.fill_ratio then
+                        elseif not internal.is_deco_biome(deco, def.name) then
+                        else
+                            table.insert(schems, { pos = pos, deco = deco })
+                            schem_placed = true
+                            break
+                        end
+                    end
+                end
+
+                if not schem_placed then
+                    local n = "air"
+                    if nt == internal.node_types.floor_deco then
+                        n = def.node_dust or n
+                    end
+                    place(n)
+                    schem_placed = true
+                end
             else
                 error(
                     table.concat(
@@ -679,12 +801,12 @@ function internal.generate_caves(data, minp, maxp)
         end
     end)
 
-    return vmanip.arr
+    return vmanip, schems
 end
 
 -- Get the noise params for the cave biome temperature.
 function internal.heat_noise_params()
-    return { 
+    return {
         offset = 50,
         scale = 50,
         spread = internal.biome_size,
@@ -715,6 +837,23 @@ function internal.is_cave_node(noise, vastness)
     return noise > 1 - vastness
 end
 
+-- Return whether a given decoration definition can spawn in a given biome name
+function internal.is_deco_biome(def, biome_name)
+    if type(def.biomes) == "nil" then
+        return true
+    elseif type(def.biomes) == "string" then
+        return def.biomes == biome_name
+    elseif type(def.biomes) == "table" then
+        for _, name in pairs(def.biomes) do
+            if name == biome_name then
+                return true
+            end
+        end
+    end
+
+    return false
+end
+
 -- Return a bool whether a position is within a given volume
 function internal.is_valid_pos(pos, minp, maxp)
     if minp.x <= pos.x and pos.x <= maxp.x then
@@ -785,6 +924,85 @@ end
 --     minetest.chat_send_all(os.time() .. " - " .. text)
 -- end
 
+-- Place all schematic decorations into the world
+function internal.place_schematic_decorations(vmanip, schems)
+    for _, schem in ipairs(schems) do
+        local pos  = {
+            x = schem.pos.x,
+            y = schem.pos.y + schem.deco.place_offset_y,
+            z = schem.pos.z,
+        }
+        local deco = schem.deco
+
+        if deco.deco_type ~= "schematic" then
+        else
+            if deco.place_on == "floor" then
+                minetest.place_schematic_on_vmanip(
+                    vmanip, pos,
+                    deco.schematic, deco.rotation, deco.replacement,
+                    true, deco.flags
+                )
+            elseif deco.place_on == "ceiling" then
+                local h = deco.schematic
+
+                if type(deco.schematic) == "string" then
+                    h = minetest.read_schematic(h, {})
+
+                    if type(h) == "nil" then
+                        error("Could not find schematic! Perhaps it the filename is incorrect?")
+                    end
+                end
+
+                h = h.size.y
+
+                minetest.place_schematic_on_vmanip(
+                    vmanip, { x = pos.x, y = pos.y - h + 1, z = pos.z },
+                    deco.schematic, deco.rotation, deco.replacement,
+                    true, deco.flags
+                )
+            else
+                error("Unknown place_on value `" .. deco.place_on .. "`")
+            end
+        end
+    end
+end
+
+-- Place all simple decorations into the world
+function internal.place_simple_decorations(flat, schems)
+    for _, schem in ipairs(schems) do
+        if schem.deco.deco_type == "simple" then
+            local pos  = {
+                x = schem.pos.x,
+                y = schem.pos.y + schem.deco.place_offset_y,
+                z = schem.pos.z,
+            }
+            local deco = schem.deco
+            
+            local i = flat:pos_to_index(pos)
+            
+            local dir = nil
+            
+            if deco.place_on == "floor" then
+                dir = flat.up
+            elseif deco.place_on == "ceiling" then
+                dir = flat.down
+            else
+                error("Invalid place_on value `" .. deco.place_on .. "`")
+            end
+            
+            local h_min = deco.height
+            local h_max = math.max(deco.height, deco.height_max)
+            
+            for dy = 0, math.random(h_min, h_max) - 1, 1 do
+                local li = i + dir * dy
+                
+                flat:set_index(li, minetest.get_content_id(deco.decoration))
+            end
+        
+        end
+    end
+end
+
 -- Helper function to convert a set of coordinates to a readable string
 function internal.pos_to_str(pos)
     return "(" .. pos.x .. ", " .. pos.y .. ", " .. pos.z .. " )"
@@ -1006,13 +1224,25 @@ end
 -------------------------------------------------------------------------------
 -------------------------------------------------------------------------------
 minetest.register_on_generated(function(minp, maxp, blockseed)
+    timer.start()
+
+    math.randomseed(blockseed)
+
     local vm = minetest.get_mapgen_object("voxelmanip")
     local data = vm:get_data()
 
-    data = internal.generate_caves(data, minp, maxp)
+    local flat, schems = internal.generate_caves(data, minp, maxp)
+    timer.checkpoint("Place caves")
 
-    vm:set_data(data)
+    internal.place_simple_decorations(flat, schems)
+
+    vm:set_data(flat.arr)
     vm:write_to_map()
+
+    internal.place_schematic_decorations(vm, schems)
+    timer.checkpoint("Place decorations")
+
+    timer.stop()
 end)
 -------------------------------------------------------------------------------
 -------------------------------------------------------------------------------
@@ -1057,75 +1287,129 @@ noordstar_caves.register_shape({
     connectivity_point = 10,
     verticality_point = 40,
 })
--- noordstar_caves.register_shape({
---     name = "noordstar_caves:cliffs",
+noordstar_caves.register_shape({
+    name = "noordstar_caves:cliffs",
     
---     noise_params = {
---         offset = 0.4,
---         scale = 0.5,
---         spread = { x = 20, y = 100, z = 20 },
---         seed = 97354,
---         octaves = 4,
---         persistence = 0.6,
---         lacunarity = 2.0,
---         flags = ""
---     },
+    noise_params = {
+        offset = 0.4,
+        scale = 0.5,
+        spread = { x = 20, y = 100, z = 20 },
+        seed = 97354,
+        octaves = 4,
+        persistence = 0.6,
+        lacunarity = 2.0,
+        flags = ""
+    },
 
---     func = function(pos, n)
---         return n
---     end,
+    func = function(pos, n)
+        return n
+    end,
 
---     connectivity_point = 30,
---     verticality_point = 80,
--- })
--- noordstar_caves.register_shape({
---     name = "noordstar_caves:donuts",
+    connectivity_point = 30,
+    verticality_point = 80,
+})
+noordstar_caves.register_shape({
+    name = "noordstar_caves:donuts",
     
---     noise_params = {
---         offset = 0.0,
---         scale = 1.0,
---         spread = { x = 30, y = 30, z = 30 },
---         seed = 3934,
---         octaves = 1,
---         persistence = 0.6,
---         lacunarity = 2.0,
---         flags = "eased"
---     },
+    noise_params = {
+        offset = 0.0,
+        scale = 1.0,
+        spread = { x = 30, y = 30, z = 30 },
+        seed = 3934,
+        octaves = 1,
+        persistence = 0.6,
+        lacunarity = 2.0,
+        flags = "eased"
+    },
 
---     func = function(pos, n)
---         return 1 - 2 * math.abs(n)^0.5
---     end,
+    func = function(pos, n)
+        return 1 - 2 * math.abs(n)^0.5
+    end,
 
---     connectivity_point = 50,
---     verticality_point = 40,
--- })
--- noordstar_caves.register_shape({
---     name = "noordstar_caves:wall",
+    connectivity_point = 50,
+    verticality_point = 40,
+})
+noordstar_caves.register_shape({
+    name = "noordstar_caves:wall",
 
---     func = function(pos, n)
---         return -0.5
---     end,
+    func = function(pos, n)
+        return -0.5
+    end,
 
---     connectivity_point = 0,
---     verticality_point = 0,
--- })
+    connectivity_point = 0,
+    verticality_point = 0,
+})
 
 -- noordstar_caves.set_world_depth(-60)
 -- noordstar_caves.cave_vastness = function(pos) return math.abs(pos.y - 60) / 120 end
 
 noordstar_caves.register_biome({
-    name = "test",
+    name = "nc:glowing_floor",
     node_floor = "mcl_core:crying_obsidian",
     node_wall = "mcl_core:sand",
     node_roof = "mcl_ocean:sea_lantern",
-    heat_point = 0,
+    node_dust = "mcl_core:snow",
+    heat_point = 20,
     humidity_point = 0,
 })
 noordstar_caves.register_biome({
-    name = "test2",
+    name = "nc:crazy_glowin_walls",
     node_floor = "mcl_amethyst:amethyst_block",
     node_wall = "mcl_crimson:shroomlight",
     node_roof = "mcl_colorblocks:glazed_terracotta_silver",
     heat_point = 100,
+    humidity_point = 0,
+})
+noordstar_caves.register_biome({
+    name = "nc:regular",
+    heat_point = 50,
+    humidity_point = 50,
+})
+noordstar_caves.register_biome({
+    name = "nc:cold",
+    node_dust = "mcl_core:snow",
+    node_roof = "mcl_core:ice",
+    heat_point = 10,
     humidity_point = 100,
 })
+noordstar_caves.register_biome({
+    name = "nc:grass",
+    node_floor = "mcl_core:dirt_with_grass",
+    heat_point = 50,
+    humidity_point = 70,
+})
+noordstar_caves.register_biome({
+    name = "nc:dangerous_lava",
+    node_floor = "mcl_core:lava_source",
+    y_max = -40,
+    heat_point = 100,
+    humidity_point = 100,
+})
+
+noordstar_caves.register_decoration({
+    deco_type = "simple",
+    place_on = "floor",
+    fill_ratio = 0.01,
+    decoration = "mcl_core:cactus",
+    height = 3,
+    height_max = 8,
+    biomes = { "nc:glowing_floor" },
+})
+noordstar_caves.register_decoration({
+    deco_type = "simple",
+    place_on = "ceiling",
+    fill_ratio = 0.1,
+    decoration = "mcl_ocean:sea_lantern",
+    height = 1,
+    height_max = 4,
+    biomes = { "nc:crazy_glowin_walls" },
+    place_offset_y = -3,
+})
+noordstar_caves.register_decoration({
+    deco_type = "schematic",
+    place_on = "floor",
+    fill_ratio = 0.001,
+    schematic = squeak,
+    rotation = "random",
+    -- place_offset_y = 5,
+})