A few years ago (about 10 in fact) I joined a page called Concept feedback which allowed users to post their webpages/app pages and get the visual design reviewed. It was actually a really very good idea and I learnt alot both as a reviewer and by having my work reviewed. I was a free lancer at the time so it was incredibly useful to have my designs eyeballed by a few others. In the end I became an expert reviewer on the page and got paid for my reviews (but that is not the point here).
I noticed that UXSE is slightly less busy than it was. I wondered if this could be an idea which would add some energy back in. Concept feedback had some mighty fine review tools (a bit like invision) where you could tag the original graphic to show which part you were talking about and the comments would be threaded. So what that would be a nice to have enhancement.
But to be honest all the basics are already here in stack exchange to do the rest of it.
If not I was wondering if anyone would like to try and start an open source version. I think it would be a valuable additional tool for the UX community globally (unless there is something like this out there now and I have just missed it).