Adding any animated images is the most annoying idea and this site is already spamed with dumb stuff so we dont need more people who will start posting shitty images under each post.
Here's my "long" answer: Animated avatars are useless and annoying. I allowed them a time ago but I removed the possibility to upload gif avatars because too many people uploaded stupid flashing avatars. They are distracting and make using this website more annoying so they are definitely a pretty bad idea and I won't allow them again. Most users seem to be clever enough to understand the problems of animated avatars when you take a look at the results of your poll.