Just discovered that Opus creates a copy of the image in the user's document folder when selecting set as Desktop wallpaper (with opus command/submenu). If it is created there to convert the image, should it be deleted after windows has received it? With name: DOpus_Wallpaper.bmp
If you delete it, Windows won't be able to load it. Windows doesn't make an extra copy and the image has to be stored somewhere.
Okay, that explains it. There is always a logical explanation when opus does something