Plist-Maker is a project mainly written in Ruby, it's free.
Ruby command line tool to generate a plist from a directory.
A simple Ruby script that creates a plist file from a directory of images or whatever.
Example: ./plistMaker /directory/of/images image_data.plist jpg
This will generate a plist called "image_data.plist" containing keys for the jpg's in the directory.
That's it. :)