Earlier quoted context omitted.
Have you tried Sigal? http://sigal.saimon.org/en/latest/ I use Jekyll for static sites but for photo galleries Sigal is my go-to solution as it is fast and stable and works very well for generating a static photo gallery. Nice work on the demo, too.
Expose looks very impressive, and was posted here 74 days ago: https://github.com/Jack000/Expose https://news.ycombinator.com/item?id=10376468
I was keen to contribute to it (to try add other template engines, caching, etc.) however it is written in bash and the script is over 900 lines and doesn't have a test suite yet. Not being too proficient in bash I was a bit anxious about diving in and contributing.