An ImageDrawing enables a DrawingBrush to contain images

   
 
<Window x:Class="Workspace.DockExample"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Workspace" Width="640" Height="480">
        <Button Height="100" Width="100" Margin="15,0,0,0">Click Me
          <Button.Background>
            <DrawingBrush>
              <DrawingBrush.Drawing>
                <DrawingGroup>
                  <DrawingGroup.Children>
                    <GeometryDrawing Brush="Pink">
                      <GeometryDrawing.Geometry>
                        <RectangleGeometry Rect="0,0,100,100" />
                      </GeometryDrawing.Geometry>
                    </GeometryDrawing>
                    <ImageDrawing ImageSource="c:image.jpg" Rect="50,50,50,50" />
                    <ImageDrawing ImageSource="c:image.jpg" Rect="0,0,50,50" />                      
                  </DrawingGroup.Children>
                </DrawingGroup>
              </DrawingBrush.Drawing>
            </DrawingBrush>
          </Button.Background>
        </Button>

</Window>