You can do it 1 of 2 ways both with conditions, wich for future refrence condition / template questions should be asked at vBulletintemplates.com
<if condition="$post[usergroupid] == X"> Show spcific icon here </if>
OR if they are in the group as a secondary member group you would use
<if condition="is_member_of($post, X)"> Show specific icon here </if>
Replace x with their usergroup id