eudc-external-viewers

eudc-external-viewers is a variable defined in `eudc-vars.el'.
Its value is

(("ImageMagick" "display" "-")
 ("ShowAudio" "showaudio"))

Documentation:
A list of viewer program specifications.
Viewers are programs which can be piped a directory attribute value for
display or arbitrary processing. Each specification is a list whose
first element is a string naming the viewer. The second element is the
executable program which should be invoked, and following elements are
arguments that should be passed to the program.

You can customize this variable.