Fans of Doctor Who will enjoy the simple, yet elegant WinterBoard theme Gallifreyan Keypad. This free theme from developer Puka1701 converts the lock screen keypad numbers into Circular Gallifreyan glyphs. Glyphs also appear in the Phone dialer, but only when numbers are pressed.
The theme integrates perfectly with iOS 7, which is required for installation. Gallifreyan Keypad is dependent on WinterBoard and only works on the iPhone and iPod touch. Once installed from Cydia, the theme can be enabled under Settings -> WinterBoard -> Gallifreyan Keypad on a jailbroken device.