Update your Bookmarks to https://sites.google.com/view/gam--commands/home
Create a list of users in a Google Sheet, where their email column header is User.
gam csv gsheet <User Email Address> <FileID> <Sheet Name> gam user ~User delete photo
gam ou "</Path/to/OU>" delete photo
This command will download the photo to the default folder (drivedir) specified in the gam.cfg file. The file name will be <User Email Address>.png.
gam user <User Email Address> get photo drivedir
Use filename '#username#.jpg' option to remove the domain from the resulting file.
gam user <User Email Address> get photo drivedir filename '#username#.jpg'
Get the photos for users in an OU and save to a spcified folder. Once run, you can use zip -r photos.zip </Path/To/Photos/Folder> to create a ZIP file of the photos for easy downloading.
gam ou_and_children </Path/To/Top/OU> get photo targetfolder '</Path/To/Photos/Folder>' filename '#username#.jpg'
gam user <User Email Address> update photo gphoto <Photo Owner Email> <File ID>