Here are 2 of the apks I've inverted for ICS so far.. I did Gtalk and Mms but xkape got those already and on my mms it has an issue caused by my apktool so I gotta fix some stuff..
Anyway, Gmail was a tough one to invert and Calc is mainly themed since it's somewhat dark stock but it looks a lot better now.. unfortunately these are 2 separate download links since I make my Gmail's data apps...
I'm guessing the easiest way is to uninstall Gmail from system first with Titanium Backup or Root Explorer, then before you reboot download the Calculator.zip and install it via recovery or if rom manager works on the GNex you can use that.. that reboot should be good for installing my Gmail as a normal app.. so it's not too bad I guess.. They've both been tested and work great... Enjoy!
1. http://bit.ly/403Gmailv2 ICS Gmail Version 4.0.3 - Fixes the undo bar messages (<b 1 b> deleted)
1. http://bit.ly/403Gmail ICS Gmail Version 4.0.3 - This should be good but report any issues
2. http://bit.ly/ICScalculator ICS Calculator - Flashable zip file
3. http://bit.ly/402ICSgmail ICS Gmail 4.0.2 - Has the Send button and stock icon
4. http://bit.ly/ICSGmail40122 ICS Gmail 4.0.1- Signed apk, Installs to data