changing login window screensaver

You need to change the screen saver for the root user.
Here is some info on how to login with root.
http://www.spy-hill.com/~myers/help/apple/EnableRoot.html

The root user is the almighty administrator for a machine. As root you can delete, manipulate, move every file of your system, even the vital ones. So if you mess things up as root your system can get unstable to the point where it is unusable. Because of that and for security reasons the root user is disabled by default.
I don't know how to change the screensaver but assume that WBW knows what he's talking about. To enable the root user do the following as system administrator (see the document WBW posted the link to):

1) Open the Terminal
2) At the command prompt type the following:

sudo passwd root

You'll be asked for your admin password to prove that you are authorized to make these changes. After that you will have to specify the new root password and have to verify it.
After that you'll be able to log in as root at the login window and change the screensaver.

Hope that helps.

floba

(MN600)

To change the desktop background of the login screen:

1. Locate System > Library > CoreServices > DefaultDesktop.jpg
2. Delete Default Desktop.jpg (you may need to authenticate as an Administrator)
3. Create an image of your own to use and name it DefaultDesktop.jpg.
4. Drag the image you created into the CoreServices folder.

Using this method you won't need to enable the root user.

He's changing the screen saver, not the wallpaper...
The system preferences before anyone logs in are the settings of the root user.

Oh, I see.

Ryan: You don't need to use the terminal to enable the root user. Open System > Library > CoreServices > Directory Utility. When the Directory Utility opens, choose "Enable root user" from the edit menu.

There's no advantage, but you will be able to change the screen saver of the login screen. When you've done that, you can disable to root user again.

When you're at the Login window select "Other", type root as username and the password you assigned to the root account. Be careful what you are doing while logged in as root!

Hope that helps.

floba

(MN601)