copy file to /sdcard & reboot to CWM Recovery.
Undo file: "tamingsari2kmms-undo.zip"
Tested on CM7.2 RC1 by vo-1 MIRACLE Edition V2 & should be work for other cm7 with achep theme.
Transparent only work for Black Background (under Mms settings)
Open Messaging -> Menu -> Settings -> Extra settings -> Tick "Black Background"