Well I know many, along with myself, make their animated avatars. I personally use Photoshop Elements thought I'm finding the version I have is both limited and glitchy. If you have Photoshop Elements I have a few sites that could help you create your own.
As to whether it has to do with any number of posts I would have to say no.
If you'd like I can attempt to make one for you, but I have to admit.. Compared to some of the amazing graphics skills I've seen on here, mine are quite limited. Either way I'd love to help ya out if you want me to. Just shoot me a PM