Since a lot of the appeal was the surprises that popped up during scenarios, there could stand to be some tweaks to preserve that.
Right now, the person setting up the encounter deck has to look at the cards to find the symbols. He'll also see the artwork, title, and maybe a bit of the description, so he has some idea what's coming. Future expansions could go with a Risk Legacy setup and separate the cards into sealed packs based on scenario; all you'd have to do is open them and shuffle them without looking. Or they could simply move the encounter cards' category icon to the very bottom or corner, so that you could glance at them without seeing the rest of the card.