Just for chuckles, I decided to try a custom image. I found a screen layout schematic for the iPhone 4s and the proper dimensions and resolution, and did this:

Not sure why the screenshot threw the logo a bit out of alignment, because on my phone, it's dead-on to the grid. And even with the schematic and prescribed values, it still took some trial and error to get the size and placement just right.

A fun exercise for a rainy morning, if nothing else. wink