Don't do what you're doing, it's against HIG
Ok, ok, I'll tell you how to do it:
You're going to want to do your own cell background views. The default grouped one is not what you want.
When a tableview asks you for a cell, set its backgroundView and selectedBackgroundView to something that looks appropriate for its place in the tableview.
Usually, this means a UIImageView with the appropriate image, though you can go wild here with a custom view, but there are gotchas.
So in your case, you would do
if (indexPath.row > sectionRowCount - 1) {
//Not the last row
//Put in the middle background
} else {
//Put in the end background
}
Then you'll want a custom table section header, but that's pretty easy.
In your case, you probably won't have to worry about when there's just one row, so that makes things even easier.