Using apple script prompt the user for an image file then set it on every desktop

select-wallpaper.applescript

tell application (path to frontmost application as text)
  try
  set imageFile to (choose file with prompt "Select an image file:" of type "public.image") as text
  end try
end tell

tell application "System Events"
	repeat with desktopIndex from 1 to count of desktops
		tell desktop desktopIndex
			set picture to imageFile
		end tell
	end repeat
end tell