Well even though it has probably been done before might I suggest a challenge revolving around superheroes?
It seems a very popular topic nowadays.
If we are going through with ..I am picking Batman

I have no idea about prizes, but I am not into these things for the prizes anyways.
Now I am always struggling timewise so if it was up to me I would have an enddate which is around the beginning of September.

As groundrules I would say:
endresult must be a rendered image, fully textured and posed( no T or zero G pose)
Superheroes only
Work in progress thread is mandatory

With regards to judging I would say a 25% vote that comes through a poll and the other 75% through 3 judges.