@pebble well zhis looks like a good minimalist solution to allow browsing a folder: https://github.com/prasathmani/tinyfilemanager

it's literally one php file and it serves a folder (by default `$_SERVER['DOCUMENT_ROOT']` but you can set it to anyzhing)

it has image previews but only when clicking on individual files, no zhumbnails as far as i can tell. it also supports arbitrary file types (unlike most gallery-focused servers i've seen) so zhe source files would be downloadable.