Snippet:-
<head>
<style type="text/css">
<!--
div#cover{ position:absolute; top:0; left:0; width:100%; height:100%; z-index:2; background-image:url(overlay.gif); image-repeat:repeat;
-->
</style>
</head>
<div style="position:absolute; top:10; left:10; width:400; height:75; z-index:1; padding:0px; border: #000000 1px solid; background-image:url(yourImage.ext);">
<div id="cover">
</div>
</div>
<!--
Much of the code on the first div can be ommitted or changed
to suit your site layout, the important part is the
div layer applied inside it, which is actually applid on
top of it
-->