Applying Nifty Corners Cubes to body?

[astralsled]

I am working on a page that utilizes Nifty Corners Cubes for some elements within the page. I noticed while making these that putting a border around it will not round the border but the corners within the border stay rounded. I thought this would be a nice effect to use for the background, to make the background image appear to be "cut out" on white.

My page is here: http://www.astralsled.com/polaroid.html

I have it all set up to show what I mean. I'd like those sharp corners of the background image to be rounded. Is there any way to apply this attribute to the body without having to make a separate layer for the "background" image, etc.?

I tried this but it didn't work:
<script type="text/javascript">
window.onload=function(){
Nifty("div#box, body","big, transparent");
}
</script>

(div#box is the little box of text at the top which works fine.)

Is this possible? Any ideas? Thanks!