NASA is amazing!

You know why? They let you download loads of amazing high quality images absolutely free, like this one, a vintage poster promoting Earth-like planet Kepler-16b, which orbits two stars. There are three different posters, you can find them here http://kepler.nasa.gov/multimedia/artwork/travelposters/

Also they provide many images taken with Hubble telescope! http://hubblesite.org/gallery/wallpaper/

If you know any other amazing sites with high resolution interesting images to download, share it in the comments below! :)