Try adding this to your body in CSS;
background-size: 100%;
If that doesn't work, add this to the top of your HTML in the body,
<div style='position:absolute;z-index:0;left:0;top:0;width:100%;height:100%'>
<img src='http://i297.photobucket.com/albums/mm215/superdude44/background-1_zps837ef0a5.png' style='width:100%;height:100%' alt='[]' />
</div>
Lemme know how it goes.