[html] Adding a background image to a <div> element

You can simply add an img src Attribute with id:

<body>
<img id="backgroundimage" src="bgimage.jpg" border="0" alt="">
</body>

and in your CSS file (stretch background):

#backgroundimage
{
   height: auto;
   left: 0;
   margin: 0;
   min-height: 100%;
   min-width: 674px;
   padding: 0;
   position: fixed;
   top: 0;
   width: 100%;
   z-index: -1;
}