XAML Playing Cards
Adam Nathan's Win32 to WinFX Blog has a good post titled XAML Playing Cards. Adam takes the playing cards from Windows XP and updates them to run on the March CTP of Avalon. As you can see in his screen shots, because the Avalon cards are rendered using vectors, they retain their fidelity even at very high zoom levels. Best of all, he includes the source code for experimentation.