Here's the scenario: you have these really cool images that have been uploaded via your rails app with the attachment_fu plugin.  You'd really love to clone those images and the generated thumbnails for use with another model but you don't want to re-upload the images and re-size them.  You can try to clone the model but that won't make a copy of the actual image files on disk (or whatever storage backend you are using).  Have no fear this code snippet may help you out (insert into attachment_fu.rb): 

      # Create a clone of an image and it's thumbnails.
      def create_clone
        c = self.clone
        self.thumbnails.each do |thumb|
            n = thumb.clone
            n.temp_path = thumb.create_temp_file
            n.save_to_storage
            c.thumbnails<<n
         end
       c.temp_path = self.create_temp_file
       c.save_to_storage
       c.save
       return c
      end

Presto, now you have a clone of the image and all of it's thumbnails with updated files in your storage backend of choice. 

Tested under Rails 1.2.3