I actually had WPF pushpins originally, but chose not to go that route. That's not to say you couldn't. In fact, I actually use an invisible (Opacity=".01") WPF button over the pushpin rendered by the map. That's how I chose to implement the ability to hover over the pushpin and get a WPF InfoBox (implemented as a UserControl). If you really want to have WPF based pushpins, just comment out line 387 in VEMap and comment out line 401 which is the call telling VE to add the pushpin.
I chose not to use WPF pushpins for two reasons. First, it seemed like overkill to render such a small UI element as a vector graphic since pushpins are typically fixed width and height. Second, due to the delay in event notification between JavaScript & managed code, the repositioning of the pushpins is a little “jerky.” So I am a bigger fan of drawing your pushpins with a vector drawing tool, and then saving them as bitmaps. You get the same visual experience with better overall perf. Your mileage may vary.