what about a contest every month? with votes ? and one theme every month? You can chose the first theme then the one who win the month contest will choose the next ! People can submit digital art or real art. people have to say where they got their brushes and all that.. they have it in the Fort Minor forums too.
It is when it's a running thread. I would do a contest every month, but I'm not very good when it comes to ideas. I could try every two months, perhaps.