I think, at least for an effect like this that would appear like it was the background of the body, some javascript would be required, ex:
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title></title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<style type="text/css">
#bgcontainer {
margin-left: 20%;
background-image: url(http://i19.tinypic.com/2mdl82c.jpg);
position: fixed;
}
#bodycontainer {
position: relative;
}
</style>
<script type="text/javascript">
(function(){
var getDims = (function(){
return window.innerHeight? function(){return [innerHeight, innerWidth];} :
function(){return [document.documentElement.clientHeight, document.documentElement.clientWidth];}
})();
onload = onresize = function(){
var bg = document.getElementById('bgcontainer'), dim = getDims();
bg.style.height = dim[0] + 'px';
bg.style.width = dim[1] + 'px';
}
})();
</script>
</head>
<body>
<div id="bgcontainer"></div>
<div id="bodycontainer">
Some content: Those accusing aces surprisedly bow to his dizzy submarines. Their admonishing swine aesthetically suffer his bittersweet tarpaulins. Their congruent acres abhorrently acknowledge her funny tables. Their horrifying swans altruistically squeak from a curious swallow. Those disgruntled animals therapeutically break our affirming aardvarks. Their cultivated tasks terrifiedly sigh over their daring students. That accommodating tetrahedron ascetically bumps his boiling thieves. Her frozen taxonomies already bubble over those frowning tautologies. Her damp aristocrats tersely admire the frustrating things. His breezy thrushes alternatively sin for her brief artists.
</div>
</body>
</html>