site_bg.jpg is 1992px wide,
footer_bg.jpg 9s 1500px wide.
That might be the empty space that you see at the right end.
You could use a css3 background-image property, but it is not widely supported, yet.
Or you could just center and repeat (x and y) the footer background image:
layout.css, Line 175
That leaves the inline containers with links in the footer left-aligned and your copyright and site link stacking to the right, also.
background: url(../images/footer_bg.jpg) repeat 50% 0;
Looks like those two categories of containers need to be centered somehow.
Let us know if you need help doing that (I'm shirking working with the grid).