If you're jailbroken on iOS 5 you'll want to check out BlurriedNCBackground, a neat little tweak that makes Notification Center that much cooler. BlurriedNCBackground simply makes the background of notification center blurry instead of the default Apple background. Once you install it there's nothing to configure. Just drop down Notification Center to see the new look.
If you want to change the blur level and customize it further you can do so via Settings. BlurriedNCBackground is available now and is a free download from Cydia.