Black isn’t the first color icon designers usually go to when designing iOS7 app icons. White is the default in the clean light asthetic of iOS7. Using a black background for your app icon can make a strong stance on iOS7 home screen.
Saturated color draws attention by carrying the most weight in the visual hierarchy of the screen. By utilizing black, you can create a strong icon with only clever typeface or simple geometric shape. Make sure to keep things simple since too much can make the small space seem crowded and confused.
Some app icon inspiration:
3. lvl cam
8. The Hunt