@Andy: to cite that image, or any photo from Commons, you can just construct it as you would any other citation from anywhere. For example:
<ref>Groeschl, George. [https://commons.wikimedia
.org/wiki/File:Battle_of_Saipan_
-_Japanese_beach_defense_GAG02.jpg File
:Battle of Saipan - Japanese beach
defense GAG02.jpg], 1944. Accessed
12 August 2023.</ref>
(By the way, you should probably change the author and date of that photo on Commons, at the moment it says it was taken in 2019 by User:GravityIsForSuckers.)
A link to the Commons image doesn't have to include the license, as it's not a re-use of the image, but it doesn't hurt to add it.
I'd recommend uploading all his photos to a category on Commons, and then linking that category from his page here on Wikitree (perhaps with one or two images uploaded here and included in a gallery, but as you say not all of them).