An iPhone Tardis Lock Screen (iOS4 or earlier)
If you're looking for a version of this lockscreen for iOS7 or later, on any iPhone, then head here. (There are also links on that page for iOS versions 5 and 6.)
This version is only for iOS4 or earlier.
If you are still on iOS4, however, then feel free to click here to download a version which works with it.
The colours look odd, but that's to compensate for the iPhone's lock-screen shading. The 'Police Box' text is missing, but that's because the date sits there.
(I stupidly deleted the original Tardis image file, and can't remember where I found it. I don't want to step on anyone's toes. If you're the rights holder and want it taken down, or credited, then please accept my apologies. It just seemed like a harmless thing to share with people, in a derivative-work-kind-of-way.)