Have a PAL 3DS now, and can say, for those confused:
The ? card launches the program in AR games. You're then given six options for six games. One of thsoe games places Miis into the real world. You can move them around with the stick and change their pose with face buttons. Sadly there's no animation - it's like static statues. You can also move around in real space to change the angle of the look you have on them, and then take photos of the Miis.
There's also a program which lets you do the same. All those cards do is bring Samus, Kirby, Mario etc out into the world. Again - static statues, and you can change their pose with the fact buttons. You can also take pictures. I managed to get all the cards/characters to appear at once, which I thought was quite cool. There's some cool sound effects from their games when the characters appear, too.
So, that's what they do. The character cards aren't games, but the character card bit - I think it's called "Star Viewer" - is one of the 'six' AR games.