You can only include images in your app if you have the right to do so. You gain the right to display images by creating them yourself, by purchasing the rights from whoever owns those rights, by complying with any license agreements regarding the images, or by use of public domain images.
There's not much special about images of famous people vs other images.
In general photographs are copyrighted by the photographer or by some entity that the photographer assigns those rights to.
Where did you get the images?