var numimages=6;
var rndimg = new Array("http://www.townandcountrytrees.co.uk/images/stories/leaves/1.png", "http://www.townandcountrytrees.co.uk/images/stories/leaves/2.png", "http://www.townandcountrytrees.co.uk/images/stories/leaves/3.png", "http://www.townandcountrytrees.co.uk/images/stories/leaves/4.png", "http://www.townandcountrytrees.co.uk/images/stories/leaves/5.png", "http://www.townandcountrytrees.co.uk/images/stories/leaves/6.png"); 
x=(Math.floor(Math.random()*numimages));
var randomimage=(rndimg[x]);
document.getElementById("contentheading").style.backgroundImage = "url("+ randomimage +")";