Like I (also in #jj2) said, the "winner may host next contest" may or may not be a good idea. The main point I was trying to make was that the contest could use some moderation, and indeed the "make original level!!1"-contest aren't attracting much participants for the very reason you mentioned - you always try to be original. That's why I'd like more specific guidelines and rules: it makes a contest more interesting.

(Original is a quite abstract and relative word too - A level full of rocket turtles would surely be original but I bet it wouldn't win an originality contest)