put this code in the header html
CODE
<!-- begin code provided by createblog.com -->
<body>
<div align="center"><img src="WEBSITEADRESS">
</div>
</body>
<!-- end code provided by createblog.com -->
replace WEBSITEADRESS with the adress to wherever you store your photos. i found a great place to store pictures that you can link to your xanga at www.photobucket.com its free too, so check it out. with the background, you can upload your picture to photobucket and then just link that for the background. hope that helped you.
Doug