Cross-posted here (not sure what devs prefer to read, the forums or the git issues):
Running latest stable update, but noticed this in previous update as well.
Steps to reproduce:
- Open “System Settings” → “Users”.
- Change user avatar to one of the stock photos provided (e.g., Konqi).
- Save and exit the Users menu.
- Reopen Users menu, notice that the stock avatar is present, but only here and nowhere else apparently.
- Log off. Notice that SDDM still uses a) your own picture, if you’ve uploaded one, or b) the default icon.
- Open the Application Launcher menu, notice same thing in #5.
There is a chance this is related to another issue, though (as seen above) uploaded avatars work, just not the stock ones.
One thing I can try is manually setting my profile to a stock image by browsing for those files in the system and pretending to “upload” them, but I have no idea where they are. I used KFind to search my system for “Katie”, for example, and either the file is named something different or my KFind-fu is no good. 
Update: Temporary workaround until this is fixed, just in case someone else stumbles upon this post and wants to use the stock avatars (my kids like Konqi and Katie 
). Credit to this reddit user who found out where the avatars are stored in Manjaro KDE.
In KDE “Users” settings, browse to /usr/share/kpackage/kcms/kcm_users/contents/img and set your avatar to one of the ones there.
You should be all set now. I’ve tested this on three machines with a few different accounts, all seems well so far.