I would like to display an image of my choice instead of the grey icon above my username on the login screen:
No doubt there is a setting for this somewhere, but I have failed to find it so far.
How do I change user images in the SDDM greeter?
Useful for testing -- you can use this command to preview the login screen without logging out.
There is a good guide for this on https://wiki.archlinux.org/index.php/SDDM#Installation
I Just kept the pic I wanted in
/usr/share/sddm/faces/
with the name<user-name>.face.icon
As per the wiki it seems only .png files are supported.This answer was provided in comment first by @yfluK
I'll suggest you look up the manual, ie. https://manual.lubuntu.me/stable/3/3.1/3.1.9/sddm_configuration.html?highlight=face%20icon
The file is located in ~ (your user directory)
Under block
[Theme]
.I named my picture
my-user-name.face.icon
, so I don't mix it with user-pictures from other users.