Imo, New Mexico plate design has knocked it out of the park once they began including that little Indian cross/sun thing (not sure what it's supposed to represent) sometime in the 1920s. The ones from the early 2000s with the hot air balloon were crap but most plates that try and incorporate an image in the background are and they had the wherewithal to abandon it, unlike many others who've embraced it.
eta: I think there's currently a push to standardize simple plates with light backgrounds and dark numbers or at the very least plates that can be read more easily by plate readers. I live in PA and they just introduced a new plate that's precisely that. I'm not particularly upset as the plate it was replacing wasn't much to look at but if I squint, it looks exactly like the California plate. And then you have Wyoming's new plate that's the most unreadable thing I've ever seen.
The plates in question: