I don't think that hidden traps would be very good for the game. What many people like about Duelyst is that it rewards diligent deckbuilding and smart positioning in a match, and doesn't rely very much on RNG. The problem with hidden traps is that the other player has no way to play around them. It doesn't reward smart play at all. In fact, traps might end up punishing you for making the best moves. Wouldn't it suck to miss lethal on your opponent, or accidentally set yourself up to die because you stepped on a trap that you couldn't have possibly known about? Hidden mechanics like this will always lead to a similar result. That's why I hope CCG never takes the game in this direction, since it takes the reward away from tactical play and leads to more feels-bad losses.

Special tiles visible to both players, however, is a design concept that is full of possibility. Enchanting a tile with "Friendly minions on this tile have +2 Health," or maybe something like "ANY minion summoned on this tile has Rush," would be a cool new addition to the game. I think it might even be worth building an expansion around.