well with your current graphic, you have strong left and right pieces, which means you would need to tile the middle.
if you modified the graphic, then you could put everything to the left, and make it fade to a tileable image, then just tile to the right ( like how we do here at code newbie )
the html would then go something like this:
HTML Code:
<!-- here's the header -->
<table border=0 cellspacing=0 cellpadding=0 width=100%>
<tr>
<td width=400><img src=images/top-left.jpg width=400></td>
<td background=images/top-tile.jpg> </td>
</tr>
</table>
did that answer your question?