12V does not help - standard LEDs still have a turn on voltage of 2.5V to 3.5V.
You could make up your over version from 12V with say 3 LEDs in series per pixel arranged in a triangle.
High brightness LEDs with 15-20,000 mcd should be plenty bright (blindingly bright even).
Buy a few from here and try them out
http://www.dipmicro.com/store/index.php?page=1&act=viewCat&catId=511
Don't stare directly at them.