The iOS artwork extractor, created by Cédric Luthi, is an iOS application that will generate png files for all artwork and emoji symbols of iOS itself, the frameworks and any installed applications.
If you have an interest to understand the inner workings of iOS, this open source project is a great place to spend some time.
Please heed Cédric’s advice:
iOS Artwork Extractor also knows how to extract artwork from apps you downloaded from the App Store. It goes without saying that this is for educational purpose only and that you should not steal others’ atwork.
If you find this stuff interesting, visit Dave Peck’s github page for his command line driven artwork extractor. Although Dave will not update the application for iOS 7, he provides some great insight into asset catalogs and .car files.