@pebble@critters.gay Simplest way? Any web server with auto-index available. Won't be pretty (just a page with links to images), but it's low maintenance, fast, and secure.

Getting a bit more complex, if you are comfortable with a bit of programming, consider writing a script to script to generate thumbnails and put together a nice index.html page. That way, the code doesn't have to be terribly high quality since it's never exposed to the internet.