I saw a few people on a Making Light thread talking about how, since a picture is supposedly worth a thousand words, they were going to try drawing 50 pictures this November, with the same spirit of "yeah, sure, this isn't my best work but I am CREATING STUFF!" One of them was doing a graphic novel, but I don't see why you couldn't set a particular goal for creating x amount of pieces of art, or one really big project, or whatever.

Sadly, there's not really a community for it, but as a writer who often finds art inspiring, I bet you could find some NaNo writers who would cheer you on in the spirit of mutual frantic creativity.