In previous versions of Qubes, I have been able to reliably set the lightdm background and i3 wallpaper by removing and re-linking /usr/share/backgrounds/default.png to some screenshotted image I liked.
Since fresh-installing R4.1.1, this behavior no longer works. LightDM flashes the new wallpaper briefly, and then fall back to the old drab Qubes_Steel background. Downstream, i3 can no longer rely on this technique.
So here are my specific questions:
How can I reliably set the lightdm background without it falling back to Qubes_Steel?
For setting i3 wallpaper, should I just rely on a utility like feh?
What is the default QubesOS path that /usr/share/backgrounds/default.png link to? I’d prefer to set it back to the system default.
This is also something i tried, with the same result. The new wallpaper appears briefly on the lightdm greeter login screen, and then quickly fades out to be replaced with the default Qubes_Steel background.
edit /etc/lightdm/lightdm-gtk-greeter.conf and make sure that background=/usr/share/backgrounds/default.png is not commented out, and there are no other uncommented backround= parameters.
Run ls -l /usr/share/backgrounds/default.png and check where it links to.
Try to remove and/or replace that file with your image (make a backup first)
The link should be /usr/share/wallpapers/Qubes_Steel/contents/images/<resolution>.png
Per my OP, this is extremely similar to what I first attempted. The difference in your solution is to replace the soft link with an actual file. Nonetheless I did try it, to be thorough, and got the same result. The image flashes briefly at lightdm greeter login, and then fades Qubes_Steel back in.
This “fading” to the default Qubes background seems to be a “transition” between backgrounds, because when I set the transition-duration (in /etc/lightdm/lightdm-gtk-greeter.conf) to something like 5000 (milliseconds), the fade happens 5 seconds after LightDM loads.
I don’t know why this transition is enabled and can’t find anything on how to disable it. So I just set transition-duration to 2 minutes (120000 milliseconds), which is long enough that I won’t ever see the fade.
Update: this workaround works for setting the LightDM background, but once I log in, the background switches to the default qubes steel. It switches to the wallpaper I have set once my window manager loads.