function changeImg(imgNumber) {
	var myImages = ["http://www.ardglassgolfclub.com/images/root/ardglass_background1.jpg", "http://www.ardglassgolfclub.com/images/root/ardglass_background2.jpg", "http://www.ardglassgolfclub.com/images/root/ardglass_background3.jpg", "http://www.ardglassgolfclub.com/images/root/ardglass_background4.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;