This is a new API from the Windows Universal 10 platform, and in this method there is only one parameter (StorageFile), you can refer to the UserProfilePersonalizationSettings class .
Until then, there is no way to set the wallpaper for win8.x application. As far as I know, there is no way to set the wallpaper as Span fit mode in the UWP software application.
Just by testing this method, it seems to set the default wallpaper to “Fill” by default.
, Windows.