Silent is Correct,
The iPhone was not intended to have any background, however we have found that if you have one icon that takes up the full screen, the iPhone would not stop the icon at any time, however, to prevent 1 icon from covering up all the others, we a lot equal size to all the icons to get a consistent feel to the buttons.
creating a background is a good deal harder than it looks as well, as you have to create the background with the icons, then idvidualy export the icon sized files in order to finish.