National geographic Photos of the Day app which cycles through the last 24 National geographic Photos of the Day.
Android 2.1+ pictures can be shown as a Live Wallpaper.
Android 4.2+ pictures can also be shown as a Daydream screensaver when your Android phone or tablet is docked.
IMPORTANT NOTE: Installing this will not give you an application icon. Both of these features are enabled in the Android settings ( Settings, Display, Live Wallpaper ...