Do you want to do a standard best run/best trick contest? Which is fine, you got to think about time requirements, judging, format (jam style? Single runs? Everyone skate one feature at a time?) sound equipment, maybe some portable shade, etc. They are fun, but i prefer watching more unique stuff.
Weird, fun, unexpected challenged, like Dime contests. Fairly objective goals that are easily judges, like height or speed. Even some side contests that anyone (spectators) can enter and have a chance of winning: most 360s, longest ho-ho, most kickflips in a row (everyone does it together, anyone who falls off their board is disqualified). Inclusive stuff, that makes it feel like a community thing as well.