At least I could manually do a 'send-to' a personal icon-generator script which manually creates the thumbnail in the appropriate thumbnail cache filename (md5_sum of file path) and refresh the window.

Would be nice if its configuration follows that of gnome-3  which is rather simple compared to others I have seen.

See my (raw) notes in
  http://www.ict.griffith.edu.au/anthony/ … ailing.txt

But I have other formats that I would like to create thumb-nailing script for, rather than simply displaying a 'generic' icon.  For Example I would like to create thumbnails for various plain text files (READMEs, logs, and other text data files etc).

In Gnome-2 Nautilus I had a special script that generated nice looking thumbnails using  ImageMagick  Works very well and was very useful with files that contained things like 'script file magic'  or text files with an internal title or time stamp.  Gnome Nautilus used schema configuration files to define thumb-nailing programs for specific mime type.

How can I add this to tumbler?  I have been unable to locate any useful documentation on it.

Is there some other method (DBus or otherwise) that can be used to generate DIY thumb-nailing in Thunar?

Some documented methods using a "XDG_DATA_DIR/thumbnailers" configuration never seem to work, (no errors or anything) so I assume these were for older versions (<1.2) of Thunar.

ASIDE: I am the web master and author of most of the ImageMagick Example Web pages. If anyone is interested I'll publish the TXT file thumb-nailer script that uses ImageMagick to generate the icon (with or without all the gnome configuration wrappers).  :-)