Ideas For A Photography Contest

I have a face book photography group that ranges from hobby shooters to professional published. They want to have a contest for the cover photo. The problem is that if judged on quality 1 of 10 members are always going to win. So I need some ideas about how to set this up in order to level the playing field. I thought about choosing three subjects (secret) and whoever submits the first photo including that subject wins. Need some ideas here please the contest starts on the first.