<Rectangle Width="150" Height="150" Stroke="Black" Margin="5,0,5,0">
  <Rectangle.Fill>
    <VisualBrush>
      <VisualBrush.Visual>
        <StackPanel Background="White">
          <Rectangle Width="25" Height="25" Fill="Red" Margin="2" />
          <TextBlock FontSize="10pt" Margin="2">Hello, World!</TextBlock>
          <Button Margin="2">A Button</Button>
        </StackPanel>
      </VisualBrush.Visual>
    </VisualBrush>
  </Rectangle.Fill>
</Rectangle>

VisualBrush myVisualBrush = new VisualBrush();

// Create the visual brush's contents.
StackPanel myStackPanel = new StackPanel();
myStackPanel.Background = Brushes.White;

Rectangle redRectangle = new Rectangle();
redRectangle.Width = 25;
redRectangle.Height =25; 
redRectangle.Fill = Brushes.Red;
redRectangle.Margin = new Thickness(2);
myStackPanel.Children.Add(redRectangle);

TextBlock someText = new TextBlock();
FontSizeConverter myFontSizeConverter = new FontSizeConverter();
someText.FontSize = (double)myFontSizeConverter.ConvertFrom("10pt");
someText.Text = "Hello, World!";
someText.Margin = new Thickness(2);
myStackPanel.Children.Add(someText);

Button aButton = new Button();
aButton.Content = "A Button";
aButton.Margin = new Thickness(2);
myStackPanel.Children.Add(aButton);

// Use myStackPanel as myVisualBrush's content.
myVisualBrush.Visual = myStackPanel;

// Create a rectangle to paint.
Rectangle myRectangle = new Rectangle();
myRectangle.Width = 150;
myRectangle.Height = 150;
myRectangle.Stroke = Brushes.Black;
myRectangle.Margin = new Thickness(5,0,5,0);

// Use myVisualBrush to paint myRectangle.
myRectangle.Fill = myVisualBrush;