People can build incredible bases in this game, but it would be fantastic if structures also had damage decals when they start getting low on HP. Things like cracks, missing parts or even fire and smoke, it think that would be extremely immersive, specially in PvP servers during raids and clan wars.
It would also be helpful for players, people could have an idea how damaged some structures are by simply looking at them. Particularly useful for both attackers and defenders in a PvP castle siege, or a player base that is being attacked and damaged by a Purge attack.