The initial log-in screen shows at least one user which can be logged into the system, with a blank photo. How can we add or change this user-image? The manual shows nothing relevant when searched for 'image', 'photo', etc.
Lubuntu 20.04 uses
sddm as its default display manager.
What you've described is the default "face" located in
The easiest way is to have an image called exactly
.face.icon in each user's home folder.
Here, I've copied over
/usr/share/icons/oxygen/base/64x64/emotes/face-angel.png to my home folder as