Latest readme explaining iOS 7.x support: http://phoenix-dev.com/Drop/README
My iOS 6 icon sizes were 12x20 for 1x and 20x40 for 2x
iOS 7 uses a height of 20 normal and 24 on the lock screen. Some example sizes from the built-in icons are:
Black_Airplane~iphone.png 12x20
[email protected] 26x40
LockScreen_Airplane~iphone.png 14x24
[email protected] 28x48
Black_Alarm~iphone.png 9x20
[email protected] 19x40
LockScreen_Alarm~iphone.png 11x24
[email protected] 27x48