Here's a list of all game jam theme generators I'm aware of online (I will add more if notified!):
- http://letsmakeagame.net/game-jam-theme-generator/
- https://cjanssen.bitbucket.io/themegen/
- https://cjanssen.bitbucket.io/themegen/themegen.html
- https://cjanssen.bitbucket.io/themegen/bmjthemegen.html
- http://baroque-creations.com/genre-generator/
- https://gist.github.com/bananu7/9252503
- http://www.ludocraft.com/gigster/index.html
- http://www.boardgamizer.com/themes
- https://orteil.dashnet.org/gamegen
- http://ygd.bafta.org/resources/game-idea-generator
- https://generateit.github.io/game/
- http://sos.gd/themes/
Obviously being fairly liberal with the concept of "game jam theme generator" to include lists of jam themes and game idea generators as well, which are just as useful I feel.