I see there is a rule that allows assets not created by yourself as long as you give credits. But am I allowed to use assets that I made for another Mech Jam that I never finished? Specifically two models, and a set of animations. Everything else would be redone from scratch. I'm considering restarting the game I tried to make last Mach Jam. But if I can't use those assets, then I'll just make a completely different game.

I don't see a reason why not to use your own assets from a previous mechjam game that wasn't finished.

Yeah of course, that’s no problem at all.