Danbooru
A taggable image board written in Rails
...The platform supports advanced moderation workflows, including user roles, content approval systems, and reporting tools, making it suitable for large-scale community-driven repositories. It also includes features such as image uploads, comment threads, favorites, pools, and wiki pages that provide contextual information about tags and artists. Danbooru is optimized for performance and scalability, capable of handling millions of images while maintaining fast search and retrieval speeds.