<style>
body
{
/*Remove below line to make bgimage NOT fixed*/
background-attachment:fixed;
background-repeat: no-repeat;
/*Use center center in place of 300 200 to center bg image*/
background-position: 300 200;
}
</style>

<script language="JavaScript1.2">
/* you must supply your own immages */
var bgimages=new Array()
bgimages[0]="http://js-examples.com/images/blue_ball0.gif"
bgimages[1]="http://js-examples.com/images/red_ball0.gif"
bgimages[2]="http://js-examples.com/images/green_ball0.gif"

//preload images
var pathToImg=new Array()
for (i=0;i<bgimages.length;i++)
{
  pathToImg[i]=new Image()
  pathToImg[i].src=bgimages[i]
}

var inc=-1

function bgSlide()
{
  if (inc<bgimages.length-1)
    inc++
  else
    inc=0
  document.body.background=pathToImg[inc].src
}

if (document.all||document.getElementById)
  window.onload=new Function('setInterval("bgSlide()",3000)')
</script>