If it comes down to a custom one, I can build my own also.
I was look for free up to about $100 for now. All it needs is customizable templates (or even just use line includes). Doesn't even need an admin panel, just read the list of sub-directories in the given directory, and list all the files displaying the corresponding thumbnails in the 'thumbs' directory in every directory. Might just be easier to make my own for now.