[gtkmm] adding a widget to a fileselection dialog.

[David Kinyanjui <david i2software com>]

hello;
I have a fileselection dialog (Selection)
and I'm trying to attach another VBox at the end or possibly an Image 
widget if is possible to do so without necessarily attaching a extra 
VBox first.
I'm not sure if this is correct because even though is not crashing, 
it's not displaying the image:

Gtk::VBox *vbox, vbox2;
Gtk::Image image;
image.clear();

vbox = Selection->get_main_vbox();
vbox->add(vbox2);
vbox2.show();
vbox2.add(image);
image.set(Selection->get_filename().c_str());
image.show();

what I'm trying to do is, since the fileselection displays the file path 
of some picture files, I need an extra widget to display a preview when 
a a given picture is selected.

Any help/ suggestion is appreciated
Thanks in advance
David