How about like this - modify the stuff in red for your particular logo:
Code:
<!-- logo -->
<a name="top"></a>
<table border="0" width="$stylevar[outertablewidth]" cellpadding="0" cellspacing="0" align="center">
<tr align="center">
<td align="center" height="178"><a href="$vboptions[forumhome].php$session[sessionurl_q]"><img src="$stylevar[titleimage]" border="0" height="178" alt="$vboptions[bbtitle]" /></a></td>
</tr>
</table>
<!-- /logo -->
<!-- content table -->
$spacer_open
$_phpinclude_output
(You may not have to modify the $stylevar[titleimage] is you are using that stylevar for your logo image path.)