My idea is this:

1) All content (e.g. textures, music, models, etc) should be procedurally generated. In other words, we take our cue from the European demo makers.

2) Game theme, anything you like, except no violence. See if you can make a game where you don't shoot something.

3) Cross-platform in the sense that it should work on at least two platforms, one of which must be Win32 or Linux.

4) Open source. We learn from each other that way.

5) No stage goals. Are we working for a company or are we doing this for fun? One thing I would like to see is the requirement to generate a tutorial or article describing an interesting techniqiue or algorithm that you used in the game. We need more articles at PGD!

6) Time frame, let's say the deadline is Xmas. Gives us plenty of time to come up with something nice, and to talk about procedural generation of content.