I am designing an app for android and iphones, there will be different editions of the app and game. Like presidential edition and celebrity edition, I need to use images of the president or celebrities, just headshots of them. My question is this legal since the president and celebrities are public figures? I will be selling the app in a app store.The images will not be actual photos, just a cutout of there face or head. Like a floating head dodging another object or another head that the celebrity was involved with. Would that be considered a parody and be ok ??