thousand of sites using these kind of contents only, like hollywood celebrities photos, and bollywood celebrities photos, but they don't have any problem with.
No, don't try to mix up adsense nearby a half adult site. Its too risky to be banned or even just them telling you later on that your not the publisher they are looking for and they disable your account.
if you want to make an adult sub forum, i suggest you make it in its own forum or site....just make an announcement there...it will be safer for you..