I like that idea, but Flickr doesn’t allow it. And since reading the rules seems to be rarer than I’d like, if I don’t restrict the submissions to 2, I get 1-6 photos per person and occasionally someone will post an illustration 10 times with different texturing or color gradients.
Policing copyright licensing already takes up the vast amount of my time, so we’d have to figure out an automated way to allow this.