I know a lot of folks are wanting to get back to Star Wars themed contests, and I understand that, but I thought I'd throw an idea out there that occurred to me while doing Christmas shopping.
I realized that the sets I end up giving as gifts most often are Creator sets, where you get instructions for multiple models. And I thought it might be an interesting building challenge to try to make a "Creator"-type set. Set a limit on the total number of pieces, and you have to make three builds from the same pieces.
Of course, on further thought, it occurs to me that such a contest would be very, very hard to "police" if people were inclined to fudge the rules, so maybe that wouldn't work.