The Last Museum
lastmuseum.com
The Last Museum is a semantic search engine for 5.8 million artworks from the world's great museums. Search by theme, style, subject, or any description you can imagine.

Per their about page-

The Last Museum is the largest search engine for museum art. It uses semantic search, allowing you to search for artworks by theme, style, subject, vibes, or any description you can imagine.

We currently have around 5 million artworks indexed, and strive to eventually index all museum art in the world.