I've never had an issue with animated avatars either...pretty much every forum has had them I've ever gone to...
If it bothers you that much:
User CP -> on the left panel under 'Settings and Options' -> Edit Options -> Scroll down to "Thread Display Options" -> uncheck "Show Avatars" -> Scroll to the bottom and save.
Voila - no annoyance.
If you don't want to do that, then install an ad-blocker extension in your browser, and add the image to your blacklist. Pretty much all ad-blocker extensions have this capability.