Just tested."1) There should not be lightgreen background with mutter."No light green background for me when running mutter --replace."2) Background might not disappear after VT switching (did not test)."The background didn't disappear for me."3) There will be fade effect when changing background."There is a fade effect.A few issues:1) The screen flashes white briefly when logging in to flashback.2) When using the Compiz session, the screen will flash black every time a window is opened or closed.3) When using the Compiz session, desktop icons cannot be shown. For instance, if you run 'gsettings set org.gnome.desktop.background show-desktop-icons true' then no icons will show up.