A good poker player should make a good spy: observant, sharp and self-controlled.
The face cards are all espionage, surveillance and cryptography themed. Many people would recognize the Guy Fawkes mask the Jack of diamonds is wearing, made famous by the antihero of V For Vendetta and the hacker group Anonymous. The Kings have James Bond spy gadget objects, the Queens have surveillance devices and the Jacks are all using puzzle/cryptography/drone and listening devices.
The Museum of Spycraft itself was a lot of fun with various tests and tasks for the visitors to do. Everyone was given a small RFID chip to carry to log in to the exhibits and it kept track of your results. At the end of the tour you would be given an “assignment” based on your results.
Unfortunately, there doesn't seem to be any hidden codes within the cards. The patterns on the backs are all the same and there does not seem to be a hidden code using anything like ultraviolet ink or patterns in the clothing or layout of the suits. I wish there were, it would really reward a sharp eye for detail.