You know, if Valve spent the time used to create trading cards to actually fix bugs, mainly the offline mode, in Steam... But I digress, aside from that, the trading cards are nifty I guess. If nothing else, should make for some badass wallpaper I don't really know anything about them, guess it's time to read up since some games I have finally support them.
Valve doesn't make the cards, they are made by the games' own devs. Aside from adding them into the daily update after the devs send them in, Valve has nothing to do with them.