function zufall(){
aBilder = new Array ("/scripts/images/1.png", "/scripts/images/2.png", "/scripts/images/3.png", "/scripts/images/4.png", "/scripts/header001.png")

var index = Math.floor(Math.random()*aBilder.length);

document.getElementById("test").style.backgroundImage = "url("+aBilder[index]+")";

}
window.onload = zufall