Yeah, I noticed that too. CustomNCBackground works, but it either has empty space on the sides or at the top (which bleeds the homescreen background through instead of your custom image).
So right now, I'm using BlurriedNCBackground, which just quite simply does what it says: it provides a blurry transparent background image instead of Apple's default background. It doesn't allow you to use your own image, though, which is what I'd prefer. But until something else comes along, it's better than Apple's background!