Regarding avatars, I agree with Spiff's comments that members don't see the majority of stuff that mods do in the background. When I was a moderator, there were so many deleted posts & spammers that I could see because of my access rights. Now that I'm no longer a moderator, my user experience is totally different as it almost appears that we never have spammers and the board flows so smoothly. I know that this isn't the case & I'm sure that this week alone, the mods removed spammers & cleaned up lots of things - it's part of the maintentance that they do on FlyerTalk to improve the experience.
Here's an example of a forum where some of the avatars wouldn't necessarily be acceptable for FT -
http://www.tfproject.org/tfp/index.php - however, they also have forum topics that aren't necessarily acceptable for FT...
That said, I'm not opposed to the avatar idea completely - though I do agree with the above comments that are not in favor of animations.