From Fedora Project Wiki
Schedule
See the following page for the F15 Artwork Schedule: F15_Artwork/Schedule
Default Wallpaper Development
Winning Concept
Alpha Wallpaper
Post-Alpha Wallpaper Refreshes
Beta Wallpaper
Post-Beta Wallpaper Refreshes
Splash Screens Development
Anaconda
Firstboot
GRUB & SysLinux
KDM & KSplash
note: These are usually done by someone from the KDE team (I believe jreznik usually makes them), but it would be nice to reference them here as well as they are part of the release graphics too!