Just general info: Avatars are just images generally in gif format. You can use any image as an avatar provided the size is <= 80 px X 80 px. So basically an animated image of that size can be used as an animated avatar.
To change avatar:
1)Click 'Profile' which is besides the Log out button.
2)Scroll down to the Avatar control panel.
3)Now you can either:
+ Upload Avatar from your machine - Browse and upload an avatar from your computer
+ Upload Avatar from a URL - Enter the url of the avatar on the internet. This stores the image in CFS.
+ Link to off-site Avatar - Enter the url of an avatar on the internet. This does not store the image in CFS and might not work if the other site experience problems.
+ Select Avatar from gallery - Select an existing avatar from the avatar gallery of CFS. YOu can find both animated and unanimated avatars here.