Hi,

I'm a bit confused about
image-dired-cmd-create-standard-thumbnail-options:

- It seems, that it's not used with pngcrush or pngnq, so this test is
  perhaps useless:
  (unless (or image-dired-cmd-pngcrush-program
              image-dired-cmd-pngnq-program) ...
- If gm is used, then the "convert" command should be added.

The attached patch works for me, but probably I'm missing something...

-- 
           Peter