Comment 4 for bug 966524

It isn't compiz. Compiz is the compositing window manager that puts all the windows on the screen. Each gnome application will create one or more GTK windows and by default the resizeable property is set to true, gnome-control-center sets it's resizeable property to false because it sizes itself according to it's content rather than allowing the user to resize it.
http://developer.gnome.org/pygtk/2.22/class-gtkwindow.html#method-gtkwindow--set-resizable
Gnome-control-centre has many panes, the appearance pane is just one of them, you will see the window resize itself as you move between them. Ubiquity the installer also probably demands to set it's own dimensions, which is particularly annoying on the map page, but that is two separate issues, one in gnome-control-centre and one in ubiquity. Neither are a compiz issue, it is just doing what the applications ask it to do.