Board Thread:Support Requests - Community Management/@comment-24995513-20140103143055/@comment-4957813-20140103144147

On the RWBY Wiki, it is on the Wikia.css page and it looks like the following:

body.ChatWindow .Rail #user-Kamikaze839 .username:after, .Rail #priv-user-Kamikaze839 .username:after { content: url("http://images.wikia.com/rwby/images/6/6c/Kamikaze839ChatIcon.png"); }

In addition, the symbol needs to at or smaller than 19x19.