Okay, this is a pretty specific circumstance, but I thought I'd report anyway.
I just played a game where I set aside a Warrior with Prince. A couple of turns later, after Prince played Warrior for me, I played a few Pawns and then another Warrior from my hand.
At the end of the turn, I wanted to exchange the Warrior from my hand, but not the Warrior on the Prince. There was no clear way for me to tell which Warrior was which in the little Exchange/Keep menu. I sort of assumed that the top one was the one from my Prince, but the rest of the Travellers didn't appear in order, so I didn't feel confident in that.
Fortunately, these situations don't seem to come up very often. It would be nice to have some kind of identification on each card to make the correct choices possible.
+1 to make it more clear;
I tripped on doing an upgrade/trash of an Urchin, while having a Prince-urchin; game trashed the wrong one.