Is it possible to get the icon file of an app (on NOT-jailbroken devices)? Could URL schemes be used to do this? Is there an API to get the icon or the only way to obtain the image is by downloading it from iTunes?
iOS apps run in Sandbox mode, which means that you can't access it's information, including icons. If you need icons, you may get it from iTunes preview page, but you will face many other problems to get it done as, for example, how you will get the list of installed apps and it's id's on iTunes.