Several professional themes were released officially on the silverlight.net site. While the raw XAML is compatible in theory with WPF, there are enough significant differences that you cannot simply drop a Silverlight theme into WPF and expect it to work.

I have taken one of the themes, Cosmopolitan, and converted it to work properly with WPF. This required removing styles for controls that do not exist in WPF, as well as modifying many styles to behave better in WPF (ScrollBar/Viewer for example).

Let me know what you think and feel free to improve on this. I have not tested all styles completely yet, so there are bound to be problems still.

You may use this however you see fit, it is license free.

View the original Silverlight demonstration here.