After some discussion, we have turned avatars on. The decision whether or not to view avatars is set per user, so you can make your own decision about it. The setting is and will continue to be OFF by default for all new users. You should check you setting to be sure it is set where you want it to be.
Currently, all but 64 users have viewing turned OFF. If you want to change or check your setting visit the "User CP" link in the upper blue menu bar, then go to Edit Options and find the "Show Avatars" check-box about mid-way down the page in the "Thread Display Options" sub-section.
To define an avatar image visit the User CP and use the "Edit Avatar" link on the left. The maximum size of your avatar image is 80 by 80 pixels or 19.5 KB (whichever is smaller). The software does not re-size images for you, so be sure it's within the limits or the upload will fail. I'm guessing the usual image formats are acceptable, JPG, GIF, PNG, but it's not documented, so try JPG if others fail to work for you--I do know that one works.
The usual forum guidelines apply to avatars as well as to text: be respectful of others & no commercial advertising images. The Moderators will delete avatars--or other images for that matter--which they decide violate the guidelines.