If you are bored of the grey background that appears in your Notification Center, then you should really try BlurriedNCBackground Cydia tweak on your jailbroken iOS device. BlurriedNCBackground tweak removes the grey linen image from the Notification Center and adds a blurry transparent background. The blurriness not only makes it easier to read stuff on your iPhone or iPad but also gives a fresh look to your Notification Center.
BlurriedNCBackground comes with several customization options too such as the ability to adjust the amount of blur, the divide ratio, and asynchronous blurring mode, which can be found in Settings.app.
You can download BlurriedNCBackground tweak for your jailbroken iPhone, iPad, or iPod touch running iOS 5 for free from Cydia. It can be found under BigBoss repo, search for it.