function changeImg(imgNumber)	{
	var myImages = ["/fileadmin/images/bigscreen/body_bg.jpg", "/fileadmin/images/bigscreen/body_bg2.jpg", "/fileadmin/images/bigscreen/body_bg3.jpg"]; 
	var imgShown = document.body.style.backgroundImage;
	var newImgNumber =Math.floor(Math.random()*myImages.length);
	document.body.style.backgroundImage = 'url('+myImages[newImgNumber]+')';
}
window.onload=changeImg;