You could use almost any modern object oriented language to do this. It depends on the Blockchain platform. For Ethereum the most popular one is Solidity but you can use Serpent, Lisp Like Language. Some ports of Ethereum even allow Python.

Yeah Ethereum did a big step forward using smart contracts. Ethereum uses the Turing-complete language to create smart contracts and stores information about the state in blockchain.

Great idea and pretty nice posters! I like that king of artwork.
One small suggestion: to add more collors to the posters.