If by profile icon you mean your Armatar(the image in the left top of your profile), you have to go to your Control Panel and then select Armatars. The Armatars that are available for you will then show up and all you have to do is select one. After that, click on Update Armatar and you'll be done.
But if you earn more Armor Points by rating games, posting in the forums etc... you will have a larger selection of armatars. But remember, don't spam or you might lose Armor Points.
Also one last bit, lately people's armatars have changed due to transition to AG3, so beware of that. Other than that this seems to be answered so now to wait for mod to do his/her work
