Anybody is allowed to post in the Public Design Post.
It's better to do that before it's finished rather than when it's finished, though, if you want to workshop things there.
You can only put it through the C3G design process if you're either A. An Ally that wins the public vote B. Or an Ally or Sidekick that buys themselves a design thread with reward points.
How do you get Reward points? Become an Ally and do lots of playtesting, take pictures, etc. to help out.
How do you become an Ally? The fastest route historically is to do a bunch of playtesting.
Posting in active design threads and collaborating in the Public Design Post don't hurt either.
That's all if you want to go the C3G route, though, of course. You seem to have more of a Valhalla aesthetic, so I'd understand if not. But if you want to go down the rabbit hole, I can promise we have a lot of fun.