Thanks, but the xfce thing doesn't seem appropriate to me, from the way that
it was solved.
The other two links are about changing a line in
/etc/xdg/lxsession/LXDE/autostart.
That line should, according to those old posts for other distros, be:
@pcmanfm --desktop
In my case it's: @pcmanfm --desktop --profile LXDE
Does that make it wrong?
In ~.config/lxsession/Trisquel-mini there's the line
@pcmanfm --desktop --profile Trisquel-mini
I can right-click on the desktop and change settings, but after restarting
it's gone.
It's not about stock Trisquel backgrounds but about personal jpg files. I
have no login screen, login is done automatically. The background there could
have been black once i got there because the system threw me out.