image-dired-display-properties-format

image-dired-display-properties-format is a variable defined in `image-dired.el'.
Its value is

"%b: %f (%t): %c"

Documentation:
Display format for thumbnail properties.
%b is replaced with associated dired buffer name, %f with file name
(without path) of original image file, %t with the list of tags and %c
with the comment.

You can customize this variable.