Cosmo Desktop serves the latest NASA astronomy pictures http://apod.nasa.gov/ to your iOS device in a few clicks.
You can let you slide and flip through all the pictures in a user-friendly manner.
If you would like to use the pictures to be your iOS wallpaper, just export the pictures to your iOS Photo Album first. You can then select the pictures at your iOS settings.
All astronomy pictures are courtesy of the NASA Astronomy Pictures of the Day under public domain, or their respective owners.
The Cosmo Desktop will always be free and ad-less. Please direct your appreciations to the APOD team by Robert Nemiroff and Jerry Bonnell http://apod.nasa.gov/apod/lib/about_apod.html
Cosmo Desktop is also available on the Mac App Store: http://itunes.apple.com/us/app/cosmo-desktop/id553916089?ls=1&mt=12