var bgimagelist = ['bg1.JPG', 'bg2.JPG', 'bg3.JPG', 'bg4.JPG', 'bg5.JPG',
                     'bg6.JPG', 'bg7.JPG', 'bg8.JPG', 'bg9.JPG', 'bg10.JPG',
                     'bg11.JPG', 'bg12.JPG'];

function GetImageSwap() {
         var j = 0;
         var p = bgimagelist.length;
         var preBuffer = new Array();

         for (i = 0; i < p; i++){
                 preBuffer[i] = new Image();
                 preBuffer[i].src = bgimagelist[i];
         }

         var url = '/images/background/';
         var count = Math.round(Math.random()*(p-1));
         document.getElementById('bgmainID').src= url + bgimagelist[count];
         if( document.getElementById('pagetitle')) { document.getElementById('pagetitle').style.backgroundImage = "url(" + url + bgimagelist[count] + ")"; }
}