As far as I know there is no copyright left on official IIIrd Reich material including pictures of all kinds for this very state (Nazi Germany if you prefer) was destroyed and did not exist after 8 May 1945 any more, and its intellectual property (including patents! Think of all the aeronautical progress...) went to the Allies. I don't know if I am formulating this quite correctly.

In any case as far as I know there is no problem at all with Signal texts and pictures. Hooray! Show us your scans!

Photographs shot "privately" by individual German soldiers using their own private cameras are another matter. I think this is private property and copyright belonging to the PHOTOGRAPHER himself and his heirs until 70 years after his death. Possessing a print or a negative doesn't give you copyright ownership (only a corresponding contract does).