I'm beginning to dabble with creating my own theme, and as a test, I made up some really quick (and awful-looking) changes for MediaPlayer, which you can see here:

Now, my play@2x.png file is a 100x100 pixel, centered image. Here, however, it shows up slightly off-center.
Anybody know why this is? My best guess is because the play button is a little longer width-wise compared to the pause...

But my real question is this - What sizes are good for changing the icons in iOS5?

Any help would be DOPE.