User avatars display on your account and when you post on different areas on Curse websites.
If you have Gravatar linked to the email you used on your account that will show up as the avatar. You may have set this up when signing up for a Wordpress account or site.
Changing Your Avatar
Like many of the settings for your account you will need to hover over the "Welcome, Account Name". Select "Change Avatar" from the drop down.
This will take you to a page where you can upload your avatar.
Click on "Browse..." and locate the avatar image from your computer. It is best for the image be square (example 100x100, 320x320, etc.) and a png or jpg (jpeg) -- sorry no animated gifs. Then click on "Upload".
Your new avatar should now be displaying.
If you upload multiple avatars they will be stored on your list on the Avatar page. You can click on any of your avatars to swap them out.