I'm taking this game design course on edX (which, by the way, is excellent) and they emphasized the importance of prototyping, and getting new/fresh people to try your prototypes.
Is it valid to ask on GD.SE "where can I find prototype play-testers for my games?"
There's a similar question here about beta testers, which appears to be closed, then re-opened.
I thought about asking people directly in chat if they are interested, but it seems to be a small pool of users who recurringly visit (not, as required, a pool of fresh people all the time).