If the app doesn't want to start after u replaced the icon, follow these instructions:
Change icon.png files for apps downloaded from App Store and they stopped working!
But the shine is really a big problem
. Some apps have an information stored somewhere, which gives the icon this shine on top. Because it is only on some of them, there must be a way to deactivate this shine option. I was told that something like this is stored in the original .ipa file, some say it's in the info.plist. Whatever, i can't edit both of these proberly. So any suggestions?