Hard to advise based on screenshots alone.
Can you upload the page and post a link so we can see the site?
Sound to me as though you are going to end up with a lot of image!
I thnk that what I would do would be to treat your current page as if it ends where it is. Add a <div> that wraps your footer. That will hold the lower section of your background image. Put a <div> inside that and make it your footer. That will contain the lower part of your content.
One solution might be to place Sky, Balloons and Meadow into one image. Use that as a fixed background.
Live example of fixed background.