var imagenumber = 10;
var randomnumber = Math.random() ;
var rand1 = Math.round( (imagenumber-1) * randomnumber) + 1 ;

images = new Array
images[1] = "./bilder/bg/bg1.jpg";
images[2] = "./bilder/bg/bg2.jpg";
images[3] = "./bilder/bg/bg3.jpg";
images[4] = "./bilder/bg/bg4.jpg";
images[5] = "./bilder/bg/bg5.jpg";
images[6] = "./bilder/bg/bg6.jpg";
images[7] = "./bilder/bg/bg7.jpg";
images[8] = "./bilder/bg/bg8.jpg";
images[9] = "./bilder/bg/bg9.jpg";
images[10] = "./bilder/bg/bg10.jpg";
var image = images[rand1];