Hi,
The supported symbol types are:
SimpleMarkerSymbol
PictureMarkerSymbol
SimpleLineSymbol
SimpleFillSymbol
PictureFillSymbol
TextSymbol
For custom symbols you could consider creating a WPF element then using RenderTargetBitmap to create an image to use as a PictureMarkerSymbol. We currently do not supported SVG symbols.
GraphicsLayer in Dynamic rendering mode should dynamically redraw the symbols to give a smooth experience when zooming in/out?
Cheers
Mike