I would personally enjoy more shopkeeper content, as well as slightly improved battle card functionality.
The shopkeeper is my favorite character in the game as far as attitude and looks are concerned. She might not be very curvy, but from her attitude you can tell she's not afraid of putting in a little more work to get things done.
The battle cards is a nice concept, but is in need of a little bit of polishing. There have been times where I wonder when my healing card is going to show up, only for it to seemingly vanish from my deck. Other times it seems it comes into play every other turn. I understand that it's somewhat luck based, but going into a battle and killing the enemy without them getting a single turn, only to repeat the same battle and not be able to kill them for three turns is slightly annoying.