var backgroundimage = new Array();

backgroundimage[0] = "images/bg1.jpg";
backgroundimage[1] = "images/bg2.jpg";
backgroundimage[2] = "images/bg3.jpg";
backgroundimage[3] = "images/bg4.jpg";
backgroundimage[4] = "images/bg5.jpg";
backgroundimage[5] = "images/bg6.jpg";

function changebg(newbgimage){
	if (document.body){
			document.body.background = backgroundimage[newbgimage];
	}		
}