The wallpaper used is *structurally compatible* with the other one,
meaning that the logo is at the same location, and not bigger.
It has one drawback: the logo is brighter, which clashes with the grub
usage. This is to be fixed with new options in grub.
Restructure the nixos-artwork to make it easy to selectively
incorporate other components from upstream without needing to download
the full package.
Until now only the Gnome_Dark wallpaper was included. Add other
wallpapers available in the package repository.
