I think we should sell bumper stickers with a picture of a couch that say: "My kid is a couch potato..." or "NO ONE CARES that your boy/girl plays soccer...", etc.
I'd have bumper stickers that have concise grammatical lessons in funny, witty comments: like an illustration someone trying to console a grieving person with the caption "Their, their."
Or, bumper stickers that state obvious facts, since people sometimes don't appreciate the obvious: for example, a bumper sticker that says, "This is a bumper sticker," or, "I'm driving a car," or, "We are driving on asphalt."