This script scales the background-image to full-screen with aspec ratio depended on your browsers window size. It also has options to be scrollable or fixed.
Donate a contribution to support the development.
Just add each snippet in each section.
new gniusBackground('myElement',{
scrollable : false,
width : 1024,
height : 677
});
<div id="myElement">
<img src="http://farm6.staticflickr.com/5060/5519822237_f016b612bc_b.jpg">
</div>
#myElement{
top : 50%;
left : 50%;
z-index : 1;
}