The following Applescript should work:
tell application "System Events"
tell current desktop
set desktopProperties to (get item 3 of (get properties as list) as text)
tell application "Finder"
In Snow Leopard, to turn this into a useful action, open up
Automator.app and from the template menu select
In the top bar, make it read: Service receives
No input in
any application. Then drag
Run Applescript from the Library pane beneath it and paste the above Applescript code into that window (replacing the default template code).
Save it as a suitably named workflow (e.g.
Show Wallpaper). This will then appear as an action in the Services menu of all applications, or you can assign it a keyboard shortcut in the
System Preferences\Keyboard Shortcuts pane under