Per Rihar:

Speaking of gangsta, this summer when I was in Austin I went to a graffiti wall that was actually several stories of concrete walls. (Stinkin’ hot there this time of year). On the highest level there was IMAO with a mushroom cloud over the “O”. I guessed it was a thinly veiled “welcome to Austin”.

Can anyone confirm/send pics?

UPDATE (from Rihar [High Praise!]):