You could make the image very large 1600x1200, with the focal point in the top left corner of the image and use no-repeat attribute with your stylesheet. That's what I did with my Twitter background
http://www.twitter.com/2createawebsite
Your CSS would be something like....
HTML Code:
{background-image: url(images/soldier.gif); background-repeat: no-repeat;}
Just remember that everyone has different browser resolutions so the placement of the focal point may be different depending on the resolution.
This is one way to do it. Maybe others have other ways.