A couple of suggestions...
1) Someone made a video clip for the Diplomatic Victory...would be nice to see it added:
View thread here
2) Many people have toyed with a Pre-Ancient Era age (Stone Age)...but none of them are Warlords compatible, and none of them are that impressive. Maybe you guys could come up with something. Would make the game much more realistic.
3) New unit: Great Settler; more of a grouping of units together, 1 settler, 1 worker, 1 archer & 1 Great Artist...but rather than being able to build it, you would be grated it for having built or accomplished something.
4) Tech improvement: Satellites; reveals the entire map to the Civ...but this is somewhat irrealistic because it only does this once when the technology is discovered, and does not reveal the location of rival Civs. In reality, Satelittes remain in orbit and are constantly taking images and updating information. So in game play, maybe the minimap can be refreshed every 5 turns or so.
5) New Improvement: Mountain Tunnels; I am thinking specifically of tunnels that span the Rocky Mountains to allow trains to pass through them. This would make the Impassable Mountains, passable.
6) New Improvement: TGV train; In Europe, there is a train that uses magnetic propulsion rather than electricity or steam. This train can get up to 300kph. It's only disadvantage is that it must remain on a contant and perfect straight track. In Civ terms, you could improve on railroads allow 1/20th movement rather than 1/10. The only condition is if the unit using the railroad needs to turn in another direction, the turn cost is 1 movement point.
7) New Air unit: SR-71 Blackbird; A plane that would have an extremely high range (something like 20 or 30) however, the only mission it could perform would be recon.
8a) Although an Air Unit has a large range for missions...it is strange that it would only have 1 movement point. It just doesn't seem right that an Explorer or several other ground units could move faster than an Air Unit. Therefore, I recommend that movements points of an Air Unit = their Range.
or
8b) An alternative to the above idea is to keep their movement to 1 point, but introduce a new technology "Air Refueling"...which would then switch Air Units' movements points to the value of their range.
9) New Wonder: The Salvation Army; This Wonder would remove 3 starvation and 3 sick (unhealthy) from every City of the Civ that builds it.
10a) Panama Canal (New Wonder): Allows Naval Units to travel across land using rivers
or
10b) Canals (New Improvement): Workers could modify river tiles to allow naval Units to move through them...the catch is that if there is a bridge built, the Naval Units cannot pass until the Draw Bridge technology is researched.
11) Animal Units: That with an early technology, we have the ability to train animal units and use them in battle.
12) New Promotion: Cargohold; Allows units with Cargo space (Transport, Carrier...) +1 to Cargo space.
13) Suburbs: Currently we can build a Cottage which grows to a Hamlet which grows to a Village then a Town. I am suggesting that a town be able to improve into a Suburb.
14) New Tradeable Item: Civ Introductions; Let's say I am playing as the Americans, and I have met the Incans and the Vikings...but neither of them have met each other. I would like a way to be able to introduce them to each other, and get a "finders fee" in the trade, either gold or technology.
That's it for now.