You can copy in the good ones from the LD11 theme list or add new themes! As a general rule, try to avoid themes that either require specific cultural knowledge (including sports), or impose implementation limitations (like “2-bit color”). Please use alphabetical ordering so it's easy to see if a certain theme is already added.
Air
Ambiguous Controls
Anthropomorphism
Avalanche
Bleeding / Leaking
Bridge
Buried
Cannibalism
Chainsaws
Chemical reaction
Circuits
Cooperation
Defense
Detectives
Dimensional shift
Dive
Draw & Paint
Ecosystem
Economy
Elastic
The Five Elements (Fire, Earth, Air, Water, Aether)
Escape
Everything's breakable
Evolution
Fans
Film Noir
Fire
Flood
Flowers
Fluff
Fruity
Gentlemen
Grapple
Gravity
Hacking
Ineffective
Inferno
Inversion
Invisibility
Jello
Juice
Kittens
Lightning
Lose to win
Masks
Mechatronics
Misdirection
Music
Orbits
Ownership
Pacifist
Pandas
Pastries
Playing Real-Life
Power
Pursuit
Procedural
Psychic Powers
Reverse/Replay
Shadows
Slavery
Space
The Tower
Time
Unbreakable
Under the City
Vi (dual-mode game-play a la vi text editing: e.g. edit & command)
Voices
Wind
X-Ray Vision
Yo-yo
(let's not use these again for a while)
LD11: Minimalist
LD10.5: Weird/Unexpected/Surprise
LD10: Chain Reaction
LD9: Build the level you play
LD8.5: Moon, Anti-Text
LD8: Swarms
LD7: Growth
LD6: Light and Darkness
LD5: Random
LD4: Infection
LD3: Preparation
LD2: Construction/Destruction (Minor Theme: Sheep)
LD1: Guardian
LD0: Indirect Interaction
72HGDC #8 Nov '06: Magnets
72HGDC #7 Jul '06: Retro
72HGDC #6 Mar '06: Magic
72HGDC #5 Jul '05: Horror
72HGDC #4 Dec '04: Swappable Parts/Customize?
72HGDC #3 Jun '04: Pirates
72HGDC #2 Jan '04: Food
72HGDC #1 Jul '03: Mindless violence
FGDC4: Ball Physics
FGDC3: Replay
FGDC2: Grow
FGDC1: Point & Click
