Some states have many different styles of plates. Oregon has several different basic background plates and depending upon which branch of the military or other causes you want to support there are about 50 different kinds of plates just for passenger vehicles.
Another vote for New Mexico. In addition to the (IMHO) near-perfect examples above, we now also have the chile plate, which loses a little in readability but is still an outstanding design:
We had a plate from some Canadian Provence that was polar bear shaped. We gifted it to friends in St Martin who display license plates in their little restaurant. It is their favorite.
Gotta give credit to the District of Columbia coming right out and putting “Taxation Without Representation” on their license plates.
(Speaking of which, I was just on a week-long drive around Lake Michigan, and a car with DC plates passed me while I was driving in Michigan. You don’t ever see a DC plate out here in the Midwest. Also, Michigan has a bunch of different plate designs … I like the one with the Mackinac Bridge on it.)