This is actually pretty easy but it took me FOREVER to figure out lol You will laugh at yourself when I tell you how..
when you hover over the costumes link at the top, a drop menu appears, go to costume administration, then click where the icon would show up next to the name of the costume you wish to put an icon to. That's the page..Make sure the pic is 200x200px though. Just like your forum avatar and main profile pic.
Cosplay DA Regular DA
Kumoricon 2014 (so far):
-Sora (Kingdom Hearts 2)
-Serena (Pokemon Y [It's the one I have lol])
-Akaito (Vocaloid. Black & Red Ver.)