$(document).ready(function () {
    var image_array = new Array("bg-main-1.jpg","bg-main-2.jpg","bg-main-3.jpg","bg-main-4.jpg","bg-main-5.jpg","bg-main-6.jpg");
	
	// Pick a random one
	var ran_number = Math.floor(Math.random()*image_array.length);
	img = image_array[ran_number]
	
	$("#header").css({
		backgroundImage: "URL(images/"+img+")"
	})
	
});