title: uwp TileContent with TileBackgroundImage does not work
body: <p>In my <code>UWP</code> app I'm using two images to test the <a href="https://docs.microsoft.com/en-us/dotnet/api/microsoft.toolkit.uwp.notifications.tilepeekimage.hintoverlay?view=win-comm-toolkit-dotnet-stable" rel="nofollow noreferrer">HintOverLay</a> property with a background image. But the tile does not show the image or or the overlay of the image. I'm using the <code>Maps.xml</code> example of official <a href="https://docs.microsoft.com/en-us/windows/uwp/design/shell/tiles-and-notifications/notifications-visualizer#:~:text=Overview,tile%20or%20toast%20notification%20payload." rel="nofollow noreferrer">Notifications Visualizer</a>. Their example works fine on my system. But the following code does not:</p>
  
  <p><strong>Question</strong>: What I may be missing and how can we make it work. I've verified that the untitled3.png and untitled4.png exist in the <code>Assets/Apps/</code> folder. I'm using <code>VS2019 - ver16.6.2</code> on <code>Windows10 Pro -ver1903</code>?</p>
  
  <p><strong>UPDATE</strong>:</p>
  
  <p><strong>Screenshot of Images junk1.png and junk2.png [size: 100x100 pixels]</strong></p>
  
  <p><a href="https://i.stack.imgur.com/GQhyo.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/GQhyo.png" alt="enter image description here"></a></p>
  
  <p><a href="https://i.stack.imgur.com/lQUxo.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/lQUxo.png" alt="enter image description here"></a></p>
  
  <p><strong>Screenshot of Solution Explorer</strong>:</p>
  
  <p><a href="https://i.stack.imgur.com/PB3hq.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/PB3hq.png" alt="enter image description here"></a></p>
  
  <p><strong>Code</strong>:</p>
  
  <pre><code>.....
  .....
  TileContent content = new TileContent()
  {
      Visual = new TileVisual()
      {
          TileMedium = new TileBinding()
          {
              Content = new TileBindingContentAdaptive()
              {
                  BackgroundImage = new TileBackgroundImage()
                  {
                      Source = "Assets/Apps/junk1.png"
                  },
                  PeekImage = new TilePeekImage()
                  {
                      Source = "Assets/Apps/junk2.jpg",
                      HintOverlay = 20
                  }
              }
          },
          TileWide = new TileBinding()
          {
              Content = new TileBindingContentAdaptive()
              {
                  BackgroundImage = new TileBackgroundImage()
                  {
                      Source = "Assets/Apps/junk1.png"
                  },
                  PeekImage = new TilePeekImage()
                  {
                      Source = "Assets/Apps/junk2.png",
                      HintOverlay = 20
                  }
              }
          }
      }
  };
  
  // Create the tile notification
  TileNotification notification = new TileNotification(content.GetXml());
  TileUpdateManager.CreateTileUpdaterForApplication().EnableNotificationQueue(true);
  
  // Send the notification to the primary tile
  TileUpdateManager.CreateTileUpdaterForApplication().Update(notification);
  </code></pre>