I've been cataloging Konami Cards for a while now and decided to add all the information I have so far on my site. Konami Cards were included with several early Konami games. Each card featured an illustration or a snapshot from the game, and the back of each card showed a serial number as well as the game's title. They were randomly included with the games and Konami produced several variations of each card (it is however not known how many different card variations were made for each game - I believe however that there was an average of six, except for Doremikka and Exciting Boxing).
I think that the list of Konami games to include such cards were:
Ai Senshi Nicol (Fds)Dracula II Noroi no Fuin (Fds)Arumana no Kiseki (Fds)Contra (Fc)
Doremikka (Fds)Dragon Scroll (Fc)
Exciting Baseball (Fds)
Exciting Basketball (Fds)
Exciting Billard (Fds)
Exciting Boxing (Fds)
Exciting Soccer (Fds)Falsion (Fds)
Getsu Fumaden (Fc)
Majou Densetsu II Daimashikyou Galious (Fc)
Meikyujin Dababa (Fds)Metal Gear (Fc)Salamander (Fc)Tetsuwan Atom (Fc)
Top Gun (Fc) Konami Wai Wai World (Fc)
Some of the above games link to a review page with pictures of such cards (located at the bottom). I'm missing a few (I know of a 6th one for Metal Gear but couldn't find a good pic, as well as two more for Tetsuwan Atom, and one more for Konami Wai Wai World). I'll also try to review the other games soon, so I can add pictures of the cards I have (I have 30+ cards not on the site yet). Although I'll update the site as I find more cards, don't hesitate to let me know if you find, or have a card not listed there.
Some of you may find all this research interesting