The whole copyright aspect of this is bunk the images are not commissioned works, they are not being reproduced and sold, the closest thing I can think of to this would be a costume contest and DC comics and Time/Warner arent going to sue Johnny for wining a bag of candy because he had a very creative homemade Batman costume. Its a matter of scale and precedence, a private individual wins a art contest with a pic of Spiderman and gets sued by Marvel and 20th Century Fox right thatll happen