The flag of Malaysia - I know, i have requested this for like ages ago. I even gave like thousands of reasons why. I'm not going to elaborate on it today since I have mentioned it before, but to simplify it Malaysia deserves to have its flag in Castle Siege especially when the number 1 player used to be a Malaysian.
Treaty Thursday - We already have Smashdown Wednesday, and Battle Friday. Why don't we have Treaty Thursday as well? On Treaty Thursday, we can buy peace treaty using Gold so we can use it later when we need to go away for a while. We shall have the choice of buying a 3 hours PT, 6 hours, or 12 hours. But we can only buy one on each day, and we can only hold one PT at a time. So whenever we have to go away for a while and we have to leave our empire, just activate the peace treaty and the empire shall be safe. Until the treaty ends of course.
Trading Post - For quite a while, people had been talking about trading resources between alliance mates. Now we can! (once this is implemented of course) With this trading system, we will be able to buy some resources that we need from our alliance mate and vice versa. The Trading Post can be built at Age 6, a Trading Post site shall appear outside of the building area allowing us to built this Trading Post.
Not only that, the TP can also allow us to buy some troops from civilisations that don't exist in CS. Like for example, I am going on a mission to destroy some emplacements for an objective. What I can do is buy several Kerambit Warriors from the the Malays via the Trading post for, let's say 7 gold each troop and when I'm training my troops, all I have to do is add them there and they'll be there to help me in the battle. I can even buy some Conquistador from Spain, or Chu Ko Nu from the Chinese. All I have to do is go to the Trading Post and we'll be able to buy the troops we want.
There's more! Emperors of an alliance can also affiliate with other alliances (max affiliation: 5 alliances) through this Trading Post so they can talk to each other in their own chat room, and even trade with each other.
That is all for my suggestions for now. I'll return if I have more ^^