Try Shimmie2. It works like the danbooru or ouroboros style imageboards. Requires LAMP stack and php-gd, and ffmpeg if you want video thumbnails.

- Stores files by md5 hash and doesn't allow duplicates.

- Database is used to store tags and support searching and is not very large.

- Can tag pictures and search by tag.

- Is fast. Can handle large number of images and large number of search results.

- Can enable pools feature and arrange pictures in a pool.

- Can enable wiki feature, which while primitive, is nice for adding notes.

- Is multiuser.