The LEGO galleries were great. I was active on the general one, and learned a lot about making MOCs from the constraction builders there. I became a part of that community with VirtualGru, BlueTorpedo, Shade, MiniGandalf, Chrisataur, and others, if anyone recalls those names. We had a lovely thing going. I have fond memories of competing in competitions with them, and I remember the etiquette of building each others' "self-mocs." Great times.
Inspired by legomaster1378 I've been tooling around on the WayBack and also remembered ToaMataEthan. I've been trying to somehow find my stuff but the chances of those pages being available in WayBack are somewhat unlikely.
Here's a page from somewhere in 2015-2016. It appears to be the only page with actual pictures that I can find. Most of the posters on this gallery were immature but there were some really talented builders (one called Promar I was always impressed with).