extensible thumbnail viewer

[Gabriel Striewe]

Hello!

I am looking for a highly customizable and extensible thumbnail viewer;
let me describe it as a kind of emacs with thumbnail viewer enbedded.

I like to extend emacs so that it enables me to use it as a file
manager. I write functions using emacs lisp so that I can execute
arbitrary commands and shell scripts on files from within emacs' dired
mode. Now, emacs does not seem to me to be great at working on large
amounts of photos this way, because a thumbnail does still give more
information on a photo than a filename gives information on a textfiles'
content.

Can anybody recommend me a photo manager and thumbnail viewer that is as
customizable and extensible as emacs?

Any hints greatly appreciated.

Gabriel