Hacker News Reader

Ah here is prior discussion on the Met release https://news.ycombinator.com/item?id=7781846

Maybe not quite in the same league and arguably of more local interest. But the ETH in Zurich makes a library of 100'000s of pictures, graphics, historical artifacts, architecture and photography publicly available.

All[1] of it in hi-res as TIFS:

https://www.e-pics.ethz.ch/en/home_en/

[1] Disclaimer: I didn't check them all, for the ones I one was involved with, the archive of historical buildings in Zurich that's definitely the case.

You could try here: https://iiif.io/community/#participating-institutions

Everyone releasing large collections tends to use the protocol. You'll find all the biggest in that list plus many more.

Paris museums, recently: http://www.openculture.com/2020/01/14-paris-museums-put-3000...

Europeana has lots, including high-res scans of the works of my favourite museum: https://www.europeana.eu/