I set a photo to be my Desktop wallpaper. Now I cannot remove that wallpaper - not even in preferences. I can remove it using Windows Setting, but I shouldn't have to.
Please add a 'Remove' or 'None' option here:
That's how you remove it, and how you've always removed it. I don't see an issue here.
Opus isn't intended to replace the entire Windows settings UI and everything you can do in it. It just has a shortcut to let you set the currently displayed image as the wallpaper.