Every release, Fedora packages up a bunch of what we call Supplemental Wallpapers. These are additional wallpapers for Fedora users to use instead of the official default wallpaper. Submissions are now open for anyone to submit a freely-licensed wallpaper. If you want to install these wallpapers on your current Fedora 20 system, install the heisenbug-backgrounds-extras-gnome package, and the wallpapers will show up in the GNOME wallpaper settings.