Ever played Spelunky?
Anyways, yeah, I could do art, if the others are serious about trying to do this. Like Sean said, though, if the art style strays out of pixel-art-territory, then I'll be pretty useless.
On the subject of what language to use, I'm not quite sure. The main question is whether any of us have the time/skill/dedication to make a game engine in C++ or something from scratch. I've been experimenting with Scirra's Construct lately, and it seems like a good, free alternative to Game Maker, for those that don't want to buy the pro version.
http://www.scirra.com/construct-classic