If code in your template is similar to standard postbit, then find this:
Code:
<if condition="$show['avatar']"><td class="alt2"><a href="member.php?$session[sessionurl]u=$post[userid]"><img src="$post[avatarurl]" $post[avwidth] $post[avheight] alt="<phrase 1="$post[username]">$vbphrase[xs_avatar]</phrase>" border="0" /></a></td></if>
and before it add this:
Code:
<if condition="$show['messageicon']"><td class="alt2"><img class="inlineimg" src="$post[iconpath]" alt="$post[icontitle]" border="0" /></td></if>