Controlling WPF Rendering

[Cairn23]

Is it possible to provide the Xaml to render a node, and if not, add it onto the to do list. I need a graph layout engine such as this but want to control how elements will look on the screen to the user such as rendering a node as a box which contains text top and bottom of an SVG icon.
There are little or no real WPF samples which demonstrate the ability's of this engine.
Another consideration is that Node is currently just a string label, could it be extended to take a generic type so that other additional data could be stored against a node and used within an overridden draw function