function bgsetup() {
	var backs = [	"back_woods.jpg",
					"back_cthulhu.jpg",
					"back_darkyoung.jpg",
					"back_grate.jpg",
					"back_stair.jpg",
					"back_wall.jpg"
				]
			
	var n = Math.floor(Math.random()*backs.length);
	
	if (typeof mainimage != "undefined") {
		document.getElementById("body").style.backgroundImage = "url('/themes/arkham/back_"+mainimage+".jpg')";
	} else {
		document.getElementById("body").style.backgroundImage = "url('/themes/arkham/"+backs[n]+"')";
	}
}