var backgrounds = new Array("preview2.jpg", "preview3.jpg", "preview4.jpg");

function randBackground() {
 
	if($('previews'))
	$('previews').style.backgroundImage = "url(images/"+backgrounds[Math.floor(Math.random()*backgrounds.length)]+")";

	setTimeout("randBackground()", 5000);

}
setTimeout("randBackground()", 5000);