Thinking of coins on notes, the Greek series has a good many examples of such issues. Some are well engraved, others (as in the German occupation series) are not so nicely done but still show lots of ancient coins. Also the India series has a large group, mostly the 1 rupee but possibly others including Hyderabad.
Then there are the National Gold Bank issues of California with their backs full of gold coins. The most interesting, or should I say controversial, is the $5 Silver Certificate that shows images of five Morgan dollar reverses overlapped in such a way that none can show the full "In God We Trust" motto. It's all there but not on a single piece. So when the question comes up, when was the motto added to paper money, is the answer 1886 or 1963?
Any others escape me at the moment but I'm sure a good many exist, and a great display could be assembled showing this characteristic.
Neil makes an interesting point about the "In God We Trust" motto. What a great trivia question!