Towels are fine as long as they are held, and aren't tied to the body or adherent to the body (eg. Danbooru post #4065442). If the second case applies, please tag as naked towel or nude cover.
Naked chocolate or other such fluids poured on a body do not count against the tag.
Ropes and belts do count against the tag. Even if used in BDSM.
Make sure you can see their crotch or lower, otherwise see nude.
