On the upper left of any Smogon forums page, you will see a bar with "Mista Rob" "Inbox", and "Alerts" as the options. Click on Mista Rob, and in the lower left of the menu that comes up, there will be an option "avatar". Click that, and you will go to a page where you can change it to something that isn't purugly.
http://bit.ly/1PFR6Ek