The LoginWindow is the window in which you log in with a username and password when you start up your computer (if you've turned off Automatic Login in the LoginWindow preferences pane of the LoginPreferences).

Q. How do I customize the pictures available for users in the LoginWindow?

A. Add TIFF(or PNG, JPEG) graphics to "/Library/User Pictures/".

Q. I need users to see my company logo/disclaimer/vision statement on startup.

A. Login Panels at ResExcellence

A. Visage

A. Put it in the login window. The login window is just a 400 x 320 graphic in TIFF format. From the CommandLine:

[localhost:~] you$ sudo cp /path/to/my_400_by_320_picture.tiff 
  /System/Library/CoreServices/loginwindow.app/Resources/loginpanel.tiff 

This seems to have changed for OS X 10.1 ... the loginpanel.tiff on my machine is much smaller -- only the blue Apple logo. You can change this, but the template display area for it is so small that it isn't much use. To change the login screen, I had to open the English.lproj/MultipleUsers.nib in Interface Builder. From there it is fairly easy to enlarge the crop area for the graphic.

A2. Another idea is to create a dummy user--then make their long name (realname is the term OSX uses) into something useful, like "Found? call 1-800-lost-mac" (YourIPis does something like this).

A3. Beyond changing the graphics, to have scripts or applications execute on every login, add LoginHooks.

A4.

[localhost:~] you$ sudo pico /Library/Preferences/com.apple.loginwindow.plist 

After the first <dict> element, add this:

  <key>LoginwindowText</key> 
  <string>Your text goes here...</string> 

Hat tip: Mac OS X Hints

Q. How does one set which background is visible behind the login window?

A. You can't, it's always AquaBlue. You can, of course, substitute another graphic for AquaBlue. It's in /Library/Desktop Pictures/AquaBlue.jpg.

See also: UsersAndGroups, LoginItems