I think the administer of the board has the option of letting us use avatars on this board.
His administrative control panel may have an option similar to this:

Enable avatars: [ ] yes [ ] no
Allow general usage of avatars;
If you disable avatars in general or avatars of a certain mode, the disabled avatars will no longer be shown on the board, but users will still be able to download their own avatars in the User Control Panel.

If he has "no" checked, then we can't use avatars.

Robb has a picture that is the size of an avatar, and he attaches it to the beginning of each of his posts.