Background images don’t scale to fit on any device by default, they’re supposed to stay in place as it is. If you want a background image to scale you can use any of the css3 features to do that if you want. Here is a little info on how to do it – http://www.sitepoint.com/css3-background-size-property/
I still haven’t got in front of an iPad just yet, so try increasing the width to the media query and see if that helps.
