As long as they have a user-made ref?

You don't even actually NEED a reference image. Lots of people did OCs without ref last time, though many of them didn't do well without. If you're in it for fun (BECAUSE WHY ELSE BOTHER, PEOPLE, SERIOUSLY) I say go for it. I didn't do a specific character this year, personally; rather, I did a historical design that I just thought was too much fun building to pass by :)

Good luck with it, whichever way you go!

I remember seeing OC's way back in 2010 and I saw some this time as well so I'm pretty sure that it's fine.

Yeah, i just wanna do for fun! It's been a while since i did a subeta contest!

(I think the last time was the Drill csc giveaway last summer)

Well thats nice to hear :)