I like the concept of graffiti done in a tasteful gilt paint. I think I would have gone with the same serifed lettering that the rest of the door was done in, though. The trick is to make it look so in character that when they remove it, they will be left with that hollow feeling inside.
How about driving a dozen head of cattle onto Juniorbush's ranch with words like 'draft dodger', 'warmonger' and 'AWOL' bleached into their pelts in a sort of natural manner?
Perhaps several real 'turd blossoms' from the Texas prairies tastefully planted on Rove's front lawn?