Updated on October 8th: As noted by one of the commenters, the original set of wallpapers don’t include what’s found on some of the newer devices. The wallpapers here were pulled from the iPhone 4. Added to the post today are the set of 23 default wallpapers that come with the iPhone 5, all of which are 640×1136 JPEG files. You’ll find them embedded below.
If you want the iOS 6 iPhone wallpapers on your own non-iOS 6 device, then you can download all of them in a single ZIP file below. They came directly from the filesystem after decrypting & extracting the root filesystem’s DMG file (/Library/Wallpaper/iPhone/).