There is a File:

src/xfdesktop-4.10.0/doc/README.kiosk

which suggests, that there are kiosk-options with which to configure locked down desktop-properties. BUT:

.../xfdesktop-4.10.0$ rgrep UserMenu src
.../xfdesktop-4.10.0$ rgrep CustomizeBackdrop src
.../xfdesktop-4.10.0$ rgrep CustomizeDesktopMenu src
.../xfdesktop-4.10.0$ rgrep CustomizeWindowlist src
.../xfdesktop-4.10.0$ rgrep CustomizeDesktopIcons src
.../xfdesktop-4.10.0$ 

none of these yields any result, and the locking down does not work. may it be, that it is documented but not implemented?

i really wanted to use this!

And xfdesktop is not the only package.
of the here (http://wiki.xfce.org/howto/kiosk_mode) mentioned config options, there are exactly three, that are working, and implemented (as appears to me)

xfce4-session-4.10.0/xfce4-session/xfsm-shutdown.c:  shutdown->kiosk_can_shutdown = xfce_kiosk_query (kiosk, "Shutdown");
xfce4-session-4.10.0/xfce4-session/xfsm-shutdown.c:  shutdown->kiosk_can_save_session = xfce_kiosk_query (kiosk, "SaveSession");
xfce4-session-4.10.0/settings/splash-settings.c:  kiosk_can_splash = xfce_kiosk_query (kiosk, "Splash") || xfce_kiosk_query (kiosk, "CustomizeSplash");

none else.

If you plan to take that out, *please* make the xfce4-settings-editor capable of locking down settings!

keep up making the greatest DM out there!

mo