Most of the really common images in iOS are tucked away in
.artwork files. These files typically contain hundreds or thousands of images, all rolled into one file. I assume Apple does this for performance reasons. If you have an iOS SDK handy, you’ll find a number of
.artwork files lying around.
My iOS Artwork Tool can both extract images from, and import images into,
.artwork files. You don’t need to be a registered iOS developer to use the tool — it’s a simple Python command-line app.
I’ve just updated the tool to support iOS6. As it turns out, a lot of things changed. There are now two different
.artwork formats: a hard-to-crack old-style format found in iOS5 and earlier, and a surprisingly easy-to-crack format introduced in iOS6. The tool now supports both formats.