There is one thing that I hate… when people join a new service and use the default avatar. Setting the avatar, signature and such makes your forum experience more personal.
There are many sites that reward you for setting a custom avatar… some sites give you points (Macheist) and others may have different rewards. For the most part the reward is that users stop mocking you.
I take custom avatars to the next level… I make mine via a method called scanner art (I scan each item on my flat bed scanner).
I know this is shorter than my mormal posts but it had to be made.