Sick stuff man.
You might try finding an art forum, they have places where you can actually auction off stuff.
I don't know any forum sites, but I remember seeing one once.
Or E-bay, Amazon?
Unless you're trying to sell it to a skater personally.

I found the left arm's detail strange in comparison to the right
with all the ripples, it's an insane amount of detail and respect for putting in work
If it's not meant to be abstract maybe think about that and proportion, the board is a little off.
It's a cool piece. I like it, just keep Progressing.