Just as a side point, a friend recently got his car sign written and, trying be be honest, informed his insurance company about it, he was then told that his insurance company would no longer insure him as they will not cover vehicles with commercial advertising on them. (and he did have business use insurance)
He tried to argue that the Honda badge on the back of the car is advertising, as is the garage's sticker in the rear window, and the tax disk holder.. and so on... but to no avail.
So just a warning, I'd check with your insurance company about this before getting it done.