Add Depends: libjxl-gdk-pixbuf
The default GNOME 46 wallpaper uses JPEG XL.
jpeg-xl 0.9 was just uploaded to Unstable with a new binary package: libjxl-gdk-pixbuf . That package is required for GNOME-ish apps to display JPEG XL images. Apps like gnome-control-center, GNOME Shell (to display the wallpaper), and the eog image viewer app.
I want to update gnome-backgrounds 46 to Unstable soon. I noticed that cinnamon has Depends: gnome-backgrounds. Therefore, I believe it would be best if cinnamon would also add Depends: libjxl-gdk-pixbuf now.