The Forest World is expected to be in 0.6.0 release. Here is list of some mediocre levels that should be definitely removed:
castle.stl - Iceberg Fortress
castledoor.stl - NOLOK
Castle_Entrance.stl (was keystodoor.stl) - Entrance to the Castle
christoph4.stl - Whatever Floats Your Boat already removed
christophD.stl - Room of Stars
CounterCurrent.stl (was christoph7.stl) - Countercurrent
dfk-level1.stl - Dark Forest Keep - The Evil Chamber
dfk-level2.stl - Dark Forest Keep - The Eyes Of Nolok
dfk-level3.stl - Dark Forest Keep - The Black Tower
dfk-placeholder-1.stl - NOLOK
diagonal_chasm.stl (was level6.stl) - Diagonal chasm (was No Name)
Duct_Ape.stl (was christophC.stl) - Duct Ape
forest1-grumbel.stl - Forest Level 1
ghostly.stl - A Ghostly World
green_hills.stl (was level5.stl) - Green Hills
key1.stl - key 1 water - to be placed behind waterfall
key2.stl - key 2 earth - to be placed underground
key3.stl - key 3 wood - to be placed in a big tree
key4.stl - key 4 fire - to be placed in a small castle
key5.stl - key 5 air - to be placed in clouds
Kneep_Deep.stl (was christophB.stl) - Kneep-deep in the depth
light+magic.stl - Light and Magic
Little_Venice.stl (was christoph8.stl) - Little Venice
Mtn_Pass.stl - The Mountain Pass already removed
Out_of_the_Cave.stl - Out of the Cave
roots_woody_roots.stl (was level1.stl) - Roots, Woody Roots
Silent_Walls.stl (was christophE.stl) - The Silent Walls
The_Origin_of_the_Ghost_Forest.stl - The Origin of the Ghost Forest
Treasure_Skies.stl (was airkey.stl) - Treasure in the skies (was In the clouds)
Two_Towers.stl (was christoph9.stl) - Two Tiny Towers
underconstruction.stl - Under Construction
Walking_Flames.stl - Walking Flames
Welcome_Forest.stl (was christoph6.stl) - Welcome to the Forest
World_of_Ghosts.stl - World of Ghosts
Level designers are always welcome to make some better levels for Forest World right now.