[Kirk Y]

Well the simplest way would probably be a template edit.

Search for in your respective 'postbit' template:

$post[usertitle]</div></if>

After add:

<if condition="is_member_of($post,6)">
<img src="images/group6member.gif" /></if>
<if condition="is_member_of($post,5)">
<img src="images/group5member.gif" /></if>
<if condition="is_member_of($post,4)">
<img src="images/group4member.gif" /></if>