Agreed, that's the lock screen. But to answer your question, you can't without a jailbreak.
Actually there's an app called iLockScreen Maker that will allow you to change the lock screen. I used it on mine and it worked fine, and I didn't have to jailbreak the device.
He's talking about the pull down thing not the lock screen
Actually there's an app called iLockScreen Maker that will allow you to change the lock screen. I used it on mine and it worked fine, and I didn't have to jailbreak the device.
We're talking about the Notification Center.
And even if we were talking about the lock screen, no app is needed to change that background.