<script type="text/javascript">
                var imgCount = 10;
                    var dir = 'images/';
                    var randomCount = Math.round(Math.random() * (imgCount - 1)) + 1;
                    var images = new Array
                        images[1] = "bg1.jpg",
                        images[2] = "bg2.jpg",
                        images[3] = "bg3.jpg",
                        images[4] = "bg4.jpg",
                        images[5] = "bg5.jpg",
                        images[6] = "bg6jpg",
                        images[7] = "bg7.jpg",
                        images[8] = "bg8.jpg",
                        images[9] = "bg9.jpg",
                        images[10] = "bg10.jpg",
                    document.getElementByTagName("body").style.backgroundImage = "url(" + dir + images[randomCount] + ")";
    </script>