You can add some simple but effective features for the game.
First thing old musics and resource gather sound effects can be added.
Game cannot allow much zoom out on x2 details please fix this too.
When you zoom out slingers and arrow shoots barely visiable it can be improved
For balancing game, armor upgrades must gives +1 armor otherwise even on early game villagers and some units being completely useless on battle.
Civilization bonuses need more balance and adding more bonus will be good for the game.
Adding new types maps and spawnable animals can be good thing for game.
Please add more units like skirmisher (game already have spear throw animation on hunting it can be easy) or bring age of mythology upgrade system example: axeman can be upgrade to champion axeman with upgraded stats and with this every unit can be usefull even late game.