I can read that changing the app icon programmatically at runtime is not possible, at least since iOS 3.0.
But... I regulary can see on "App" websites apps that can put icons on the springboard. The first I remember is that kind of app that you give a friend's picture from your album, and it creates an icon so you can call him just clicking on that icon:
http://itunes.apple.com/fr/app/speedtouch-the-best-home-screen/id378360978?mt=8
http://itunes.apple.com/fr/app/desktop-shortcut/id421701004?mt=8
http://itunes.apple.com/fr/app/appbutler-app-organizer/id327391626?mt=8
http://itunes.apple.com/fr/app/tap4music/id365578914?mt=8
So I guess, is it still impossible to change the app icon programmatically at runtime?
Update
Apple have changed this, you can do this now: https://developer.apple.com/documentation/uikit/uiapplication/2806818-setalternateiconname
Original Answer