We have published a new Expression Interactive Designer tutorial targeting the January 2006 CTP. It's called ImageButtons . Here's the overview:
Because Windows Presentation Foundation (WPF) is based on the .NET Framework, you can customize the functionality of existing control types. You can start with a control defined in a WPF library, derive a new control type from it, and build that into a library of your own. You can draw a control onto the design surface of Expression Interactive Designer just as easily whether it is implemented in your own library or in a WPF library. In this tutorial you will extend the Button control to create an ImageButton control which has a Source property in addition to the standard Content property. You can then specify how the new Source property is to be used by the control by modifying the control's template.