"For if a man mints many coins from one mould, they are all alike, but the Holy One, blessed be He, fashioned all men in the mould of the first man, and not one resembles the other..." (Babylonian Talmud: Sanhedrin 38a)
Every Roman emperor minted coins bearing his own image. During the minting process, each coin was stamped so that the resulting coins would all look alike.
God created Adam in His image and has been minting new men and women ever since. Though there may be some close resemblances between family members, no two of us are exactly alike. There are no limits to the number and diversity of "coins" that God can create. Thus God displayed his supremacy over the rulers of the earth.
So when Jesus pointed at the coin and said "Give to Caesar what is Caesar's and to God what is God's" (Mark 12:17), his audience might have been familiar with some other rabbi's teachings. Every coin belonged to Caesar, but God put his own divine stamp on us.
I like the thought of God minting me like a shiny new coin, stamping me with his hand, and assigning me value.