Do you guys realize that the costume will be edited before they add it to the miracle shop? I believe the contest is not about all being professional graphic designers, but being creative and giving ideas. As you can see, some of the works aren't even pixelized.. just sketches.
Yes, he may have copied one of the costumes and didn't give any credits to the authors, but still.
As it was said, everyone has his own opinion. Some costumes are liked by many but disliked by twice as many.
Anyways, here is my suggestion. Developers could make a vote for a costume (among the winners) to be added, if the players really want that (cause they are the ones who are eventually going to pay for the costume).