In my case, they look something like this. (You can see a zoomed section of the poster below).
Yesterday I re-installed Plex after a year away from the software, and have been quite impressed: there are no options that require fiddling with, and fewer keyboard commands to remember. The installation process for the Mac media server is also a great deal smoother, as the software picks up movies, television shows and music the first time it runs.
It took a few hours for the software to completely scan my droboPro for all its media, but once the process was finished I once again had a single central library from which to peruse my collection.
Plex has changed its database format, so I could not employ the technique I used previously to pull out the movie covers; instead, I used the rather excellent Plex Export to do so. I fed the resulting movie covers to another piece of great free open source software (MacOSaix) together with a target image of Ms Jolie, and tweaked the result to create the poster you see above.