GNOME 42 needs two wallpaper pictures – for the default (light)
colour scheme and for the dark one. Because we are clearing out
the paths in `gsettings-desktop-schemas` to prevent closure
from bloating, we need to set them in the NixOS module.
Since the wallpaper for the default colour scheme is dark,
will relegate it to the dark colour scheme and switch
to a light blue variant for the default colour scheme.
That one has inverted roundel for the NixOS logo but
it is the only light-ish background that has the logo
of the same size and placing as the dark wallpaper.
7eb14b532a