Icon before Usernames

[Andrej]

Hello,

I want to put an icon (a star, a medal, a key, etc.) before usernames that are in a premium user group (for example). How can I do that?

Here is a example from a MyBB forum:

 

[Paul B]

Add some CSS mark up to the user group.

See this for more details: http://xenforo.com/help/user-groups/

And these threads for examples:
http://xenforo.com/community/threads/username-effects.4914/
http://xenforo.com/community/threads/usergroup-markup.5506/

 

[Andrej]

Thank you Brogan. I tried searching before posting, but I have searched for wrong terms.