Icon2ImageLite is a utility for creating image thumbnails of file, folder and disk icons in various image formats, in batch, among other features.
This functionality is available as a contextual menu in the Finder. An accompanying system preference pane enables you to specify the sizes of generated images, in a range from 16 to 128 pixels square.
Icon2ImageLite is part of the Limit Point Software Utilities Bundle : http://www.limit-point.com/Utilities.html. Purchase a Utilities password to activate all the utilities, including Icon2ImageLite. Updates are always free, new products always included!