[Opserty]

 <tr>
        <td style="padding-bottom:0; background:url(/path/to/my/image/cat_$forumid.jpg) no-repeat;" colspan="<if condition="$vboptions[showmoderatorcolumn]">5<else />4</if>" height="50">
<a href="forumdisplay.php?$session[sessionurl]f=$forum[forumid]"><img src="/path/to/my/image/clear.gif" width="100%" height="50" border="0"></a>
    </td>
<td align="center" style="padding-bottom:0;">
            <if condition="$childforumbits">
        <a href="#top" onclick="return toggle_collapse('forumbit_$forumid')"><img id="collapseimg_forumbit_$forumid" src="$stylevar[imgdir_button]/collapse_tcat{$collapseimg_forumid}.gif" alt="" border="0" /></a>
            </if>
        </td>
    </tr>

Try adding that bit in green I've highlighted.