Dear Maintainer,

When I choose theme-debian-breeze in sddm configuration, the wallpaper didn't
show and I have a white wallpaper in place.

Regards

It's not a (current) bug, it's just that there may be files of on older package
version in the theme directory that have not been uninstalled and are now
obsolete and obstructive.
(One option would be to uninstall the package, manually delete its remaining
remnant and reinstall it again.)