The current (and quite probably evolving) policy on NSFW images in the darkroom is that they are allowed. As I said, the policy is likely to evolve, so if you have opinions on the matter please go here to make your voice heard. I want to avoid having to split up things into a NSFW subforum if at all possible, so what we are going to try for now is some self regulation.
If you don't mind or even encourage NSFW images being posted to a thread that you start please include the tag [NSFW-OK] in the thread title. If the thread title does not contain that tag you can't post NSFW images to the thread, even if you put it behind a spoiler box. You can still link to them, but the links should be labled as NSFW so no one gets a surprise. Err on the side of caution here, since we want to keep people from getting into any sort of trouble accidentally.
I know that this doesn't solve all the issues with NSFW images in TDR, but it's a start.