[bentley]

Standard Ebooks has a database of public domain oil paintings for use as book covers. SE is strict about copyright clearance and requires either scans of a copyright‐expired publication containing the painting, or an explicit statement from a reputable museum that the work is CC0. Here’s an entry I contributed:

https://standardebooks.org/artworks/arthur-i-keller/calvin-c...

[robin_reala]

To be specific, this is US public domain only (which is globally non-standard).

[graemep]

Nothing is globally standard.

On the other hand they do allow search by century and very little from the 19th (and none earlier) century is still in copyright anywhere.

There is a possible problem with countries where a photographer can have copyright over their photograph of an earlier work. Again, there is not global standard.

[RobotToaster]

>There is a possible problem with countries where a photographer can have copyright over their photograph of an earlier work.

To be specific, Germany is one of the few countries where this applies https://en.wikipedia.org/wiki/Threshold_of_originality

It's an absolutely stupid idea IMO.