yeah boobs are just boobs. we all have em, females just have bigger ones. I don't even think tasteful full-frontal nudity would be inappropriate. Not that I'm going to go paste naked women pics in here or anything, but if I drew a naked angel or something or posted one of those anatomical reference studies where the model is nude, i don't think that would constitute "pornography". It's not my forum of course but I'd think a good guideline on nudity would be that the nudity itself was not being used strictly for sexual arousal but for some other purpose (art, reference, etc...).
...except in the case of boobs, since the latest boob pics obviously weren't meant for anything but enjoyment.
I could see how a spread legged naked pic could be inappropriate. (well, not so much inappropriate as much as there's no reason for it to be Here, when there's billions of other places to see that sort of thing)