r/3Dmodeling is the most active 3D art sub I've found. r/Simulated is more VFX, but it's really cool to check out the top posts of all time. r/shittysimulated is VFX again, but really funny. I've found others, but they're not as active as r/3dmodeling.
Here are all the 3D / game art related subreddits I know of, so probably one or more of them will be what you're looking for (I searched on Reddit and found them all about half a year ago, so some new ones may have appeared since):…