Honestly, I don't think it's a big deal. And there isn't anything gross; the pictures all come from the show itself so again, nothing worse than T'Pol's butt crack...and the captions aren't anything you can't say on broadcast TV. Yes, there's some sexual innuendo, but nothing blatant, and I think maybe we're just a little gun shy because at the site where this originated, we were half-playfully admonished for taking the caption thread into the gutter...though the person begrudgingly admitted that it *was* pretty funny.
Really, if a few posts ago we could talk about Trip's "package" and "junk," and an mod was one of the people doing it...*shrug* Using that as a barometer, I don't think anything we've come up with is much dirtier than that.
Now, these same pictures and captions were met with enthusiastic hilarity at yet another forum. My opinion is, it's a matter of personal preference, but nothing that should be rule-breaking.