You can change the footer position to relative and instead of using the bottom property, set the top property to -250px or whatever you want. Set the z-index property to -1 to get it behind the wrap.
Take a look here: http://jsbin.com/picazedu/1/edit
EDIT:
A better solution, to avoid the footer being displayed in the middle of the window, is applying the background image to the body and adjusting it with the background-position:bottom left
property. Now you can give the footer
the height you want to fit the background image where you want: http://jsfiddle.net/YQMyc/4/