Hi Stephen,

* The Layouts TreeView would probably looks better when putted in a GtkFrame

I will try.
 
* Maybe is better to keep consistent with the other gnome/xfce tools and
drop the flags images (using text only in the TreeView).

I'm a real maniac about icons, I want icons in all menus if possible and in all lists
because I find much faster to read icons than strings, so somebody have to
patch my code before integrating in lxpanel I can't do this :)
 
* The Show Layout as should use a combobox, to be less cluttered

The bad in a combobox is that you cannot see all options at first glance.
I think that when the options are few (only two in this case) the radiobutton is better.
 
* The Keyboard Model button may be on the same line of the label
(pack_start the label and pack_end the button), and should be with no
relief (gtk_button_set_relief (GTK_RELIEF_NONE)).

If the button has no relief the user could even not realize it's clickable,
an exception is in the panel where everything is expected to be clickable.
About buttons in line with the button I will try.

Cheers,
Giuseppe.