There really aren't any hardened-fast rules about avatars. No nudity / drugs / language are the obvious ones. For the most part we want to keep the board "family friendly," meaning a broad cross-section of people, and not necessarily G-rated stuff.
The blatantly obvious boobs were stopped a while back because I and some other people Mod the board while at work and that's not OK to have on the screen if a coworker drops by.
Here's the avatar in question at the moment:
I tend to be more cautious than most, so I'd ask him to replace it with something a little less obvious. Anyone else?
A lot of people will find that funny, like me. But I don't want my granddaughter/nieces to see that when they look over my shoulder at the monitor and I have to explain it. They are 8-13 and I'm not comfortable having to explain anything like that to them whatsoever