All of these contain "questionable" content at some time or another with the exception of the last link so be careful. iv.83net.jp - Sometimes contains questionable porn images (or if you're persistent enough you can find the latest wapka on it but I haven't seen anything in awhile). up24.ayame.jp - Is flagged on multiple browsers as of recently so yeah... my.wape.ru - Place to download images/videos (with an 18+ section) charm.i.ng - model/jb/porn board hiqqu.xxx - New-ish user-contributed porn/hentai site?
some of these have post restrictions you can get around with proxy4free.com
or pick one from www.listproxies.net also works ok.
up25.ayame.jp is the updated link for 24 and is no longer "flagged" by browsers but there isn't much on there often worth DLing these days...