Image validation in the list editor can take quite a long time if there are a lot of items in the list. Consider removing it entirely, and have xfdesktop make sure images are valid on demand instead.
Useless comment: I think you should. Validate before showing, that's enough.
ok, i removed the image validation from the list editor, and xfdesktop makes sure the images are valid on demand, and fixes up the .list file if not.