Bliss is a light theme that provides gray icons for all system icons plus some apps; it also includes a lock screen with a slender slider (lock screen may not work in some cases).
How to Install:
1. Jailbreak and install Cydia + WinterBoard
2. Search Cydia for “Bliss” and install the theme
3. Open WinterBoard and select Bliss
4. Tada! Your new theme should be working perfectly. If not, check off SummerBoard Mode in WinterBoard.