Neal is the definitely a legend.
Here is a couple more pieces I found, the Spidey one is totally Neal I'm not sure about the Joker one, it has his "style" but if his studio did it, it could have been any of his clones.
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I know he sells an artbook when he does the comic convention rounds that had lots of art from the Universal resort, I've seen a few of the actual drawings themselves a few years ago. I remember seeing a Batman attraction and a weird Joker coaster with a high point being a huge Joker hitting the car with a giant mallet. I should have bought that book when I saw it, I can't remember why I didn't......