codice:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Documento senza titolo</title>
<style type="text/css">
<!--
#container {
	background-attachment: fixed;
	background: url(bg.jpg) no-repeat;
	background-position: 100px 100px;
	padding: 0px;
	height: 400px;
	width: 400px;
	border: 2px solid #000;
}
-->
</style>
</head>

<body>
<div id="container"></div>
</body>
</html>
Ovviamente devi modificare le misure in base alle misure del tuo div e della tua immagine di sfondo, ma il concetto resta lo stesso