Takes the path to the current background image from System Events and takes the file name out of the path.
If you have a second monitor, you need to find the com.apple.desktop.plist file. It's in /Library/Preferences/ or /Users/yourusername/Library/Preferences/. Then use QuickLook to display it. There will be several keys in the key "Background" (They will be named like "475863654"). Locate your second monitor by looking at the background image names in those keys. Remember the 9-digit name of the key (e.g. "475863654") and use things like Dashboard or Stickies to copy it since QuickLook doesn't allow copying. Open the script and change the "default" in the script with the number you found. It may sound a little difficult because of my bad explanation but it isn't.
Enjoy.
