It depends on the situation for me, but in general I say no. I personally take pride in my avi for portraying what I like rather than a quick kii that gets other members bothered.
aside from the fact they look tacky as hell and are usually LQ, i don't think they should be allowed. such a desperate attempt to be funny, and sometimes they can be a tad insensitive.
Lethal posts flamebait comments in Britney threads that they LEAP into and co-sign the Hive mocking mental illnesses but as soon as someone has obviously fake pics of Bey in their avatar it's a problem
All this over the bad Beyonce pics you didn't like
Why dedicating so much for the artist you hate?
so I'd say yes. As long as it's not too crazy