You may submit 2 deviations per folder per day. The Features folder is closed and I'll move pictures in and out to keep it pretty/impressive (I keep an eye on the deviations submitted so if I see a good one I'll add it.. )
Mature content, tentaclelegs and mermen are all fine.
You can submit to the favourites folder - and please do!
The featured folder is for the 'best' work - submissions subject to approval or moved there by me. (Actually, if you submit it to that folder, I'll accept it and then move it if I choose, rather than declining and having you resubmit to another folder etcetera)