ORIGINAL: Arjuna
.....you want a bigger picture frame and you're volunteering to get the necessary larger public domain images.
As you can see on the screenshot dazkaz15 posted above, you have to quote the German Federal Archive ("
Bundesarchiv") as source and add the signature of the picture (identification code i guess, eg.
Bild 101I-127-0391-21, where "Bild" means "picture", plus you have to add the name of the photographer (last name is sufficient, if it's known). In theory, reproduction is allowed without permission, if the conditions above are met.
Also, with all the pictures and reels stored in the NARA archives, US governmental institutions are both pretty lax (when it comes to copyrighted material obtained in/from other countries) and pushy (by imposing their views on other countries), if it comes to copyrights of material that's more than 60 years old.
While US institutions boldly declare material that had been either confiscated (eg. in Germany, Japan, and other countries) or collected 60+ years ago to be part of the public domain pool, there still may be companies, institutions, or individuals who are still rightful/legal owners of the respective copyrights, according to European/German/foreign laws.
US companies that are incorporating such material into their products (for commercial use) often don't care about such foreign copyrights if their products are being distributed in the US only.
But since the Slitherine Group is active in the UK, thus inside European legislation, and since copies of Matrix Games are sold to individuals or resellers residing in the European Union, copyright limitations or special licensing (like for Bundesarchiv content) should be
- a) respected,
- b) researched,
before taking "bigger pictures" from the supposed "public domain" pool and incorporating them into a commercial product.
I still advise to contact the Federal Archive for infos regarding reproduction within a commercial product (like a game).