Now many of you have no doubt noticed a few of the animated avatars on the site.
You may have noticed that the majority of them are terrible.
Souplex is here to help improve your lives, as always.
Rules for making a good animated avatar:
1. The motion should loop well. Otherwise there's that awkward frame where it jumps back.
2. No moving camera. Otherwise it's disorienting when it jumps back.
3. Keep the animation short. It's obnoxious if it drags on for too long.
4. No obnoxious bright flashes.
5. Keep it contained to one shot.
Follow these simple rules and you'll do fine.
You're welcome.
Captcha: it is fair
Edit: Really, what you should ask yourself first is; "Should this be animated?" Most animated avatars are animated for no real reason. You're just making an already slow site load slightly slower.
Unless being animated adds something other than being animated, don't do it.