I spent the last 3 hours trying to figure out how to change my lock screen background to something other then that fireworks screen. Just in case anyone else is looking to do the same thing here is how:
cd to /usr/share/backgrounds/beefy-miracle/default
you can either change beefy-miracle.xml to point to a file of your choosing, or go into the subfolder and replace the correct .png file with one of your own. For instance, I have a widescreen laptop so I just went to /usr/share/backgrounds/beefy-miracle/default/wide and overwrote the beefy-miracle.png file with an image i liked.
sudo cp /usr/share/backgrounds/gnome/FootFall.png beefy-miracle.png
If anyone else knows an easyier way to do this, or a more "correct" way I would love to know what it is.
I also changed the gdm background to the footfall image. Steps below:
sudo -u gdm dbus-launch gnome-control-center
Then just choose your image.
I cant take credit for that one though, google took me to that answer: http://forums.fedoraforum.org/showthread.php?t=279492