In header template
You'll have
<td align="$stylevar[left]"><a href="$vboptions[forumhome].php$session[sessionurl_q]"><img src="$stylevar[titleimage]" border="0" alt="$vboptions[bbtitle]" /></a></td>
Change to
<td align="$stylevar[left]"><a href="$vboptions[forumhome].php$session[sessionurl_q]"><center><img src="$stylevar[titleimage]" border="0" alt="$vboptions[bbtitle]" /></center></a></td>