function updateBG(loop) {
	var now = new Date();
	picurl='bg-image.php?'+now.getTime();
	preload_image = new Image(400,400); 
    preload_image.src=picurl;
	document.getElementById('bgimage').style.backgroundImage='url('+picurl+')';
	if (loop) timerID = setTimeout("updateBG()", 5000);
}

// next launch
//timerID = setTimeout("updateBG(true)", 5000);