To specify a new picture to use as the background for the login screen, open up Terminal and type…
defaults write /Library/Preferences/com.apple.loginwindow DesktopPicture /path/to/image
If you don’t know the path, instead of typing it, just drag the image you want into the terminal window.
To revert back to the default picture…
defaults delete /Library/Preferences/com.apple.loginwindow DesktopPicture
Did some digging in the snow and this is what happened. See a few more photos in this album.
After awhile an iPhoto library and the Pictures folder can get quite cluttered with pictures from many sources. One way that can make this easier to handle is to use multiple libraries to keep things separated. I use three different ones myself. To create a new one or switch between different ones, just hold down the option key while opening iPhoto and a dialog box will prompt you for what you want to do.
However, switching between separate libraries using this method can quickly get to be a pain. I’ve written an AppleScript to help with this. Download the iPhoto Library Launcher, open it in the Script Editor, modify the libraryPath to refer to your library, and then save it. iPhoto won’t allow you to have multiple libraries open simultaneously, though the script should detect if another library is already open. If that’s the case, a dialog box saying “About to quit iPhoto!” will pop up and the user can choose to cancel or continue. If no choice is made within five minutes, the script continues launching the new library.
In Mac OS X it’s pretty easy to switch users with the Fast User Switching icon in the menubar. However, if you wish to do it via the Dock or via a keystroke, you need to create a small AppleScript. This comes in handy for me when I want to log into the GUI as root. Since the root account will not show up under the menubar icon, you can use this to attain easy access to it. See this Apple Support article to learn how to enable the root account. Warning! Don’t use the root account if you don’t understand it!
First, open Universal Access control panel in System Preferences and check “Enable access for assistive devices”.
Next, download the AppleScript User Switcher.
Open the script in the Script Editor and modify the password and username to suit your needs.
Save and you’re done!
The original script and process was found at Mac OS X Hints. I’ve modified it slightly above.