For starters, add additional Levels to the game, making sure that each additional level is more challenging that the one that precedes it.
Refine the game's skill Level rating by assigning a different rating for each level the player successfully completes.
Modify the game so that it displays an icon in the System Tray whenever it is minimized. Provide the ability to redisplay the game when the player clicks on its System Tray icon.
Create a splash screen for the game and use the PictureBox control to include a suitable graphic image.