Here's the latest version of my NineGrid element, along with a sample program that demonstrates how it works with both vector drawings and bitmap images.  The code hasn't changed much since it was posted here last month, but I've renamed the Padding property to BorderThickness, included comments, and added features to the sample application.

To use the NineGrid element, simply add the NineGrid.cs file to your project, make sure you have the proper namespace mapping in your XAML markup, then add a NineGrid element:

<Window
 xmlns=http://schemas.microsoft.com/winfx/2006/xaml/presentation
 xmlns:x=http://schemas.microsoft.com/winfx/2006/xaml
 xmlns:local="clr-namespace:NineGridSample">
    <local:NineGrid BorderThickness="40,40,40,40" Source="ShadowBorder.png"/>
</Window>

Enjoy!

--Eric Stollnitz