Entre <head> y </head> pone esto:
<style type="text/css">
body{background-image : url(fondo.gif); background-attachment : fixed;}
</style>
<table width="100%" border="0" cellspacing="0" cellpadding="2"><tr><td align="center"><a href="http://www.cicpm.org" target="_blank"><img src="http://www.amsystems.com.ar/imagenes/fw/firma2.gif" border="0"></a></td></tr></table>