Considerable imaginative and technical skills may go into creating such avatars. These avs tend to be similar in basic design with slight variations to differentiate each one from the others. It reminds me of the songs in some bird species. The species identifies itself and its members by a basic template that serves as the collective song. Yet each individual bird adds a small unique variation to that template in order to signify its individuality.
Animated avatars contain motion, such as an eye tearing, a bird flying, or a flag waving.
Tapping a finger, blinking one's eyes, banging one's head against the wall - there are infinite expressive possibilties.