I think there's a lot of interesting ideas in your message. One in particular that caught my attention:
It could be pretty Epic to have some sort of 'pygame community game'.
A few years back, I tried to make a collaboratively developed text adventure game which I called Weatbag, for 'Written by everyone all together, the big adventure game'. It didn't really go anywhere, but I learned that the idea wasn't new - people called such games Multi-User Dungeons, or MUDs. I still think it could be a really fun idea, and I'd be interested to see it extended to a game with simple graphics.
The idea with Weatbag was that the user could move between squares on a NESW grid, with the information about each square stored in a separate module. Any square which didn't already exist could be claimed by submitting a pull request to add something there. I wonder if it would be possible to do something similar with a graphical game? Maybe with a collection of sprites and textures to use so people could compose a simple scene without having to create new artwork?
Maybe this could be a fun project for a future pyweek or something - put together enough of a game to be playable, and build a framework for outside contributors to easily extend the game after the contest.
Thomas