Comment 6 for bug 1460303

https://bugs.launchpad.net/lightdm-gtk-greeter/+bug/1458330

It's bug in greeter, not in settings application.
There is a small regression due to 2.0.0 => 2.0.1 update. Greeter doesn't work correctly with some gtk themes. It will be fixed in next release.

As temporary workaround - edit this file:
/usr/share/themes/Clearlooks-Phenix/gtk-3.0/applications.css

Add following line at the end:
#screen.lightdm-gtk-greeter * { background: transparent; }

> after installing the GUI tool it does not appear in lxpanel menus
I'll check, but usually it located in "Preferences" submenu.