It depends on what device you're targeting. If you looking at just the iPhone 5/5s then you're spot on. If you're also taking into account everything below the iPhone 5, then you will also need
320x480 (non retina)
640x960 (retina)
So it just depends on the devices you're supporting. There are loads of resources on the net about these things. Also bear in mind that the background size will be different depending on what components you use, such as navigation bars and tab bars. And also if you're supporting iOS 7 then the status bar is transparent, where as on iOS 6 and below, you don't need to provide the background for that (so the above dimensions are actually correct for iOS 7 but not exactly right for iOS 6)