images = new Array();
images[0] = "http://www.abcprint4me.com/mockup/images/header_bk1.jpg";
images[1] = "http://www.abcprint4me.com/mockup/images/header_bk2.jpg";
images[2] = "http://www.abcprint4me.com/mockup/images/header_bk3.jpg";
images[3] = "http://www.abcprint4me.com/mockup/images/header_bk4.jpg";

function showImage() {
	var index = 0;
	var current_image = new Image();
	index = Math.floor(Math.random() * images.length);
	current_image.src = images[index];
	document["head_image"].src = current_image.src;
}