GNOME 42 introduced a dark style preference, and with it, support for
combined light/dark wallpaper pairs. Unfortunately, there's no easy way in
GNOME to add your own wallpaper pairs—until now!

Dynamic Wallpaper makes it easy to select a wallpaper to use with the
default style and a different wallpaper (e.g. a nighttime version) to use
with the dark style. Choose a name, save your wallpaper pair, then find it
in GNOME Settings → Appearance → Background.