MyBB Community Forums

I seem to be in a bind, one of my clients has asked for me to use PNG images for the Messenger icons that appear under the username, this is normally no problem, but I cannot seem to find which template the needed bit of code I need to change is in.
if someone would be so kind as to help me out that would be much appreciated.

So you just want to change the image for the usergroup, right? For example: Admin, Moderator, etc.?

actually I've been asked to change it globally for a single forum style. Last I knew that was possible.