I have several hundreds of Windows Media Video (.wmv) files on my
PHP/MySql/Linux server. I would like to find an application
(preferrably PHP) which can show snapshots/thumbnails and statistics
of these .wmv files.

I have found a few items out there for linux which can do this:
The main being here http://ffmpeg-php.sourceforge.net/

I haven't tested them as I run windows servers but you will also need
this to be installed:
http://ffmpeg.sourceforge.net/index.php

The PHP function can gather much information about the given files,
such as bitrates, frames, titles etc...

If you have any problems compiling the source code: google for compiled versions.

I would actually reccomend that you comiled PHP from scratch with this
but its totally upto you (don't actually know if you have these
permissions???)

Good look

<a href="http://ffmpeg.sourceforge.net/index.php">ffmpeg-php<a/> will
work for most movie types however ffmpeg doesn't support Windows Media
9 movies so it will only work if your movies have been created with an
older version of WMV.

-Todd Kirby (developer of ffmpeg-php)