Choose 20 Images From A Set Automatically?

Does anyone know of a program that will allow me to setup a batch so that it will work through a directory, containing sub directories of images files, pull 20 pics, and save them to a new folder.. one for each of the dirs?

Some of the existing directories have over 100 full sized pics in them, whilst others have 25 or so, therefore it would be nice if there was also an option to choose the pics from about half-way through each sub dir or, randomly, thats not a deal breaker though :)

Regards,

Lee