A former APT student of mine, Sunny Kharbanda, has really been diving into the whole 'cartoons in CG' experimenting. It's a lot of fun seeing him find new things. Since we're both tinkering in this area we communicate a lot, sharing what we find works, what doesn't, etc. Sunny just posted on his blog about his process for developing the backgrounds to work with his animation tests (you can see those here and here). Cool stuff. Check it out.