<esri:MarkerSymbol x:Key="SymbolIDName" OffsetX="15" OffsetY="28">
  <esri:MarkerSymbol.ControlTemplate>
    <ControlTemplate>
      <Canvas Width="35" Height="35">
   <Image Source="ImageSource" Width="30" Height="30"/>
   <TextBlock Foreground="White" Canvas.Top="-8.5" Canvas.Left="22" Text="{Binding Attributes[LabelAttribute]}" />
      </Canvas>
    </ControlTemplate>
  </esri:MarkerSymbol.ControlTemplate>
</esri:MarkerSymbol>