Custom statusbar icon library for iOS 4.x and later
Source code and instructions are available at GitHub
Icons should be placed either at:
(3.x style, 4.0-compatible)
/System/Library/CoreServices/ SpringBoard/Default_.png
/System/Library/CoreServices/ SpringBoard/FSO_.png
or
(4.x only)
/System/Library/Frameworks/ UIKit.framework/Silver_.png
/System/Library/Frameworks/ UIKit.framework/Black_.png