Change the login window background picture - revisited

Jun 14, '07 07:30:00AM

Contributed by: dt@qserve.de

As I found out in some forums (i.e. this ancient Mac OS X Hint), the common way to change the login window's background picture is to replace the Aqua Blue.jpg in /Library » Desktop Pictures with your own image. However, there's a more elegant way to do this: by adding a value to the appropriate plist file, namely /Library » Preferences &raquo com.apple.loginwindow.plist. You can do this in two ways, either with a Terminal command or by directly editing the plist file using Property List Editor from the Xcode package.

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.

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Mac OS X Hints
http://hints.macworld.com/article.php?story=20070610164328933