Just a Few Suggestions...

Here's a list and explanation of a few things I think would make the game more fun:

1) More Varied Terrain - currently there are only oases, cities, and fortified points on the map. Why not add stuff like lakes, rivers, and mountains/highlands? Then there could be more of a strategic choice to place cities, as follows:

Rivers/Lakes - Troops traveling across these (maybe ships would have to be built first, with each ship being able to hold so many troops) would have a reduced travel time, especially so if their target was right by one. Ships could not be used for hunting or attacking oases (explained below).
Islands - Less than four or so "squares" big, these would exist in lakes and wide rivers. A player could claim an island as their own by building a city on it, and no non-allied players could build on it. Obviously, there would be a large demand for islands, so perhaps there could be a limit as to how many one could own at a particular level, and/or islands could be constructed (limit on that also to avoid river/lake filling) for an insane amount of resources. The disadvantages to being on a island would be that you could not occupy oases or hunt on the mainland from a city on one, as ships could not be used for that. There could be an oasis or two on the island with you (perhaps you could choose the type(s) if you built the island) but that would be it.
Mountains/Highlands - Cities built on these would receive a defense boost, as it is harder for enemy troops to climb up to it. However, attacks coming out from cities so positioned would take longer to reach their targets.

2) Outposts - These would essentially be mini-cities. Unlike cities, you could resign from an outpost and it would disappear. There would be a limit on how many outposts you could build per level, just like cities. The difference between outposts and cities would be that outposts would have no resource buildings, traps & turrets, or ability to train troops. It would be basically a semi-permanent base for your troops, who would be dependent upon the city the outpost-building party was first sent from for food. Attacks against oases/other players could be launched from an outpost, but you could not hunt from one. To prevent troop obliteration, when an enemy attacks your outpost to capture it (it would be like an oasis - you win one battle, you get it), your troops would not be killed, they would be "driven out". The battle would proceed like an ordinary battle, except that at the end, the losing party's troops are sent back to the city from which they came, taking as much time as an ordinary dispatch (to prevent immediately using move city to take out the troops when they appear back home). One could dispatch more troops to an outpost as long as they own it, but they would first have to go through the city from which it was originally built (so all the troops could return to one place if you lost the outpost).

Obviously, this would take a loooooong time to implement. Heck, it might not even possible to do the varied-terrain thing, and if it was done, I would suggest giving each player either the coins to or a special one-time privilege to move each of their cities a single time after the upgrade was completed, lest you want an underwater city! But the "outpost" feature would be something I personally would very much want.

If I think of more, I'll edit this, and for anyone else, please post any questions/counter-suggestions/ideas you may have!

I believe both have these have been suggested before, but outposts were camps