OK... let's say you do have someone helping the judging...whatever....and you've gotten the artists to submit all the work they've done on this project of yours, and The Grand Prize is......
The selected art will then be painted on my car and all images will be posted back to the sites where the contest is run.
Psssst...The posting on the original sites could be (and is, daily) done on the sites anyway without you being the middleman, and who says they'll pass Moderation?
Wow. Are you sure you can afford that? Won't you need some large corporate Underwriting for this undertaking?
And here I was thinking April 1st had come and gone. 
I wonder what will really happen to those images.