Jun 14, '07 07:30:00AM • Contributed by: dt@qserve.de
Terminal solution:
Open Terminal and type these two commands (the $ is the command prompt; don't type that):
$ sudo -i
$ defaults write /Library/Preferences/com.apple.loginwindow \
DesktopPicture '/path/to/replacement/image/file.jpg'
Replace the /path/to... bit with the full path and filename of the image you'd like to use.
Property List Editor solution:
Launch Property List Editor (in /Developer » Applications » Utilities), and then open the com.apple.loginwindow.plist file from /Library » Preferences. Add a New Sibling of class String with the name DesktopPicture. In the Value column, enter the complete path to the new image you want to set as the login window backgroung image. For example, you'd use this...
/Library/Desktop Pictures/Plants/Agave.jpg
...to use the Apple-supplied agave plant picture. Please keep in mind that you need the correct user permissions to edit the plist file; save the changes and quit the editor when done. After using either method, log out and you should see your new login window background picture.
I found out that this was possible by exploring the /System » Library » CoreServices » SecurityAgentPlugins » loginwindow.bundle » Contents » MacOS » loginwindow executable in detail.
