Until now (unless I'm mistaken), when I wanted to customize the lock screen wallpapers, I used the gnome-tweaks application.
However, I recently noticed that on the Appearance menu, this option no longer appeared:
Is this an anomaly? Should I proceed differently, and if so, how?
Or is it no longer possible?
Thank you in advance for your help.
penny-farthing Which Solus edition are you using? Budgie, or Gnome?
I use Budgie Desktop.
penny-farthing
Probably I have misunderstood your issue. At first I though you were trying to change wallpaper in Login Window, so I am replaying to this. The best tool for this is lightdm-settings app.
In "Background" section you can change your login window wallpaper and make sure to disable "Draw user backgrounds" option, because it overrides login window wallpaper.
Open the dconf-editor. Go to org.gnome.desktop.screensaver.picture-uri. In the Other value field, enter the path to your image.
E.g.:
Rememberfile:///path/to/image.jpg
Thanks for your feedback.
I think we misunderstood each other and I probably didn't express myself well.
I wasn't talking about the login screen, but the lock screen: when you click on the User Indicator button, then on Lock to lock the user session, the wallpaper appearing to unlock it may be different from the one used back on your session or from the one on the login screen.
And it seemed to me that you could change this before in gnome-tweaks.
It is indeed OK to do this, thank you.
But so, the session lock screen change applies to all users of the computer.
Now, it seemed to me that previously with gnome-tweaks, each user could customize their own lock screen (I don't think I dreamed it).
In the latest release, this feature has been discontinued. You can install the old version, e.g.: sudo eopkg it https://cdn.getsol.us/repo/shannon/g/gnome-tweaks/gnome-tweaks-42-37-1-x86_64.eopkg
Great, it was that. 
Thank you for your feedback, which has answered my questions, so I'm closing this post.
