Splitting out the desktop-backgrounds part of 1247747, for clarity. f23-backgrounds landed already so that bug should be closed, but desktop-backgrounds has to be updated to depend on it or else GNOME does not use the F23 background image. Note: this is not sufficient to fix KDE; KDE has its own fXX-kde-theme package which also needs bumping. See https://bugzilla.redhat.com/show_bug.cgi?id=1251241 .
desktop-backgrounds-23.0.0-1.fc23 has been submitted as an update for Fedora 23. https://admin.fedoraproject.org/updates/FEDORA-2015-12884/desktop-backgrounds-23.0.0-1.fc23
desktop-backgrounds-23.0.0-1.fc23 has been pushed to the Fedora 23 stable repository. If problems still persist, please make note of it in this bug report.