There's not a css for this. I think you have already seen the
body{background-repeat:repeat-y;}
The problem would be that this will not work for all resolutions if you have a fluid design. But maybe this suits your needs.
You can use the previous css plus this div
body
{background-image:url('bg.gif');
background-repeat:repeat-y;}
#bgdiv
{background-image:url('bg.gif');
background-repeat:repeat-y;
background-position:top right;
width: 100%;
height:1200px;}
the height of the div and the name of the file are just for educational purposes