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.
Best Answer
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.