These images are packaged into .apk files. These apk files are then stored in /system/app or /system/priv-app
For this you will need to learn Android device themeing. The images aren't standalone and they are present in specific files. The file or files you are looking for is the framework-res.apk or systemUI.apk.
If you need help with theming let me know.
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iOS7 Kik Messenger | Svelte UI CM11 Theme | Active Launcher