Your link list, your rules. I'd talk to the webmasters you're specifically doing trades with first and, if they object, dont do it.
Ultimately, if you're treating it as a sponsor ad/link, then i"m sure its fine.
It seems a fair amount of other webmasters have an ad of some sort there.
http://www.tommys-bookmarks.com/cumshots.shtml
http://www.outlawsporn.com/cumshots/
Just be sure to contact your current traders
I'd personally make sure it was ok first.