I posted this in the Diamond forums but wanted to share here too...
there is a new manila editor that has functions for simple manila replacement/theme creations as well as cooked roms... much more accurate than the original Manila Editor
As I posted earlier in the "Today Screens" post there is a new manila editor program available at XDA from Chainfire.
http://forum.xda-developers.com/showthread.php?t=470798
I've tried this as well as Manila Editor 2.0.. this Chainfire one is perfect! I only suggest you work from a copy folder so you don't lose your originals.
Be sure to read the "manual" post for how to's and what if's.. but its pretty straight forward, allows a viewing background color so you can see those white qtc's and repairs/fixes headers etc for those hard to replace items.
Have fun and post what you've created!! I'm fixin to redo my flyfishing icons so they are cleaner.. I really had to jig around to make them import in Manila Editor... this program will be a breeze compared!