Good luck with your displates, friend! I have the same publicity concerns as you mention; I have no Facebook/Instagram/Twitter and very limited online presence in communities and groups. So far, I've had 10 sales (8 medium and 2 large ones); the commission is very small indeed, but it is totally passive income. Nonetheless, I am now seeking some contacts that can promote my displates through their social channels.

The other thing I tried is makersplace.com :)