Something like this:
Can I start a contest in the Comic Contests forum?
Generally speaking, the winner of a comic contest starts the next one in the series. So the winner of Comic Competition 75 chooses the theme for and judges Comic Competition 76.
If you have a good idea you can initiate a new type of competition (for example, the Mystery Comic Cup to the Tag Team Comic Cup). We'd suggest that you hang around for a few months and see how things work before you try that.