[Nightfall4]

I think the member contest would be interesting. I do see the problem though you would have verifying if the members were actual new "real" members and not fictitious accounts. That same could be said for any contest though. It is difficult to prove the author's authenticity of the item submitted for the contest.

Another concern is certainly the costs of the prizes. If it is all coming out of your wallet, then it adds up after a time. So that raises the question what kind of incentive will get people to enter that is affordable.