Can you use the promo terrain (Tower of Sorcery, Herdstone) as terrain pieces that can be picked in a game, or can you only use them with their special scenarios?
Question about promo terrain
House rules would allow you to do whatever you want, so I would go that route with friends who are like-minded.
If you are playing "officially" I would think that promo terrain would be frowned upon, but with no tournament life in the game, it should be simple to just clear it with your opponent before hand and see if he also wanted to use it.