Hi everyone,
I know this question is nearly a decade old, but the issue still somewhat exists in KDE plasma 5. So the background part is just a little annoying because you will need to set it in two places:
1) systemsettings > Desktop Behavior > Screen Locking > Wallpaper

This is half the battle. Click "All Settings"

2) Startup and Shutdown >Login Screen (SDDM) > Background
Change the background here as well.

If you want to change the login icon you're going to have to do a bit of a work around.

Click "All Settings"

1) Account Details and change your picture

Now for the fun part! In a terminal:

cd ~/

sudo cp .face.icon /usr/share/sddm/faces

cd /usr/share/sddm/faces

mv .faces.icon User.face.icon

This puts your home space icon in the faces folder for SDDM.

Better late than never I guess I hope this future proofs the problem.

the current situation is that the main login screen is provided by SDDM, while users' lock screens are provided by Plasma. I know they made efforts to try and provide a unified look-and-feel, but there certainly seems to be room for improvement.
It would probably be worth bringing this up as a new topic in the Visual Design Group forum.

For the current requirement to copy the user's icon into SDDM's faces folder, https://github.com/sddm/sddm/issues/174 has some discussion around the issue, but it looks like SDDM should use ~/.face.icon, if available/accessible.

It also seems reasonable to have the lock screen default to the background used by SDDM. Perhaps submit a case to bugs.kde.org.

Avatar

KDE Reviewboard: Load user's avatar from AccountsService if it exists - https://git.reviewboard.kde.org/r/128951/

Created Sept. 19, 2016 and submitted 5 months, 3 weeks ago

At here Arch Linux so using: https://wiki.archlinux.org/index.php/SDDM :

Changing your avatar
You can simply put a png image named username.face.icon into the default directory /usr/share/sddm/faces/. Alternatively you can change the default directory to match your desires:
/etc/sddm.conf
[Theme]
FacesDir=/var/lib/AccountsService/icons/

=> Setting the 'FacesDir=/var/lib/AccountsService/icons/'

Testing:

Starting the KDE User Manager and setting the user Avatar:


Restarting the plasmashell.

The Kickoff Avatar is right:



The lock screen Avatar is right:



The SDDM with the /var/lib/AccountsService/icons/ could need a symlink from user-name to user_name.face.icon

The SDDM Avatar is right:


Seems to work at here with the

KDE Frameworks: 5.32.0
KDE Plasma: 5.9.4
KDE Applications 16.12.3
SDDM 0.14.0

There is a patch available to fix the root cause of the problem here:

https://github.com/sddm/sddm/pull/684

Is there any possibility of KDE Neon having this patch applied to v0.14.0 of SDDM?

jchoksi wrote:There is a patch available to fix the root cause of the problem here:

https://github.com/sddm/sddm/pull/684

Is there any possibility of KDE Neon having this patch applied to v0.14.0 of SDDM?

Neon - Bug 371232 - patch sddm to fix avatar: https://bugs.kde.org/show_bug.cgi?id=371232