[Gtk-sharp-list] Creating Custom Controls?

[Zak]

First off, I'm a complete GTK newbie.  I've done quite a bit of
ASP.NET and SWF development in C# and VB.NET, but I'm not sure how
applicable that is... :)

Anyhow, I want to create a custom control.  To begin with, it should
behave just like a CheckButton only instead of a box that gets checked
and unchecked, I would like to toggle between two different Images. 
Eventually, I will be extending it with more functionality...

So my question is - where do I start? :)  Is there some easy way to
build this by deriving from some existing control?  If so, what class
do I extend, what methods do I override, etc?

Thanks!
-- 
-Zak