I just updated to El Capitan 10.11 and I'm already being flustered with issues. How do I change system icons (mail, messages, finder, launchpad) to the default icons I had prior to the update? I can no longer go under Applications then Get Info and copy paste my image. It simple won't let me do this for system icons (it will let me do it for non-Apple applications, though). Anyway I can do this without jeopardizing my system?