My wallpaper changed as well. It now shows a wide black stripe on both sides, as well as 13.2.rc1 displayed diagonally in the upper right corner of the screen. I removed the unrelated packages, this is what upgraded here.
Start-Date: 2014-07-12 09:15:27
Commandline: apt-get dist-upgrade
Install: grub-theme-siduction-december:amd64 (2014.07.11, automatic)
Upgrade: siduction-art-ksplash-december:amd64 (2014.01.26.1, 2014.07.11)
siduction-art-kdm-december:amd64 (2014.01.26.1, 2014.07.11)
siduction-art-wallpaper-december:amd64 (2014.01.26.1, 2014.07.11)
siduction-art-kde-december:amd64 (2014.01.26.1, 2014.07.11)
End-Date: 2014-07-12 09