I have created a “Critics Corner” category on Unofficial3DForums for artists who are looking for constructive criticism about their art and their craft. Your NSFW art is welcome so long as it’s tagged appropriately. (Porn however is not.)
Edit: When I originally created the “Critics Corner” I forgot I already had a sub-category created under Showcase called Critical Corner. Oops!
In any event, feel free to use #showcase:critical-corner to post any works-in-progress or any finished works that you’d like honest feedback on. Like I said, #nsfw is welcome in this sub-category (porn is not) but please tag appropriately.