What do different shapes for unit icons mean?

[Racington]

Why do some units have a square icon, while others have a circle? And then military units and army commanders have a sort of pentagon shape. I can't find any information on what the different unit flag icons is conveying.

 

[gdr_willter]

Banner Shape Pentagon with 1~3 Vs below = Military Unit (Number of Vs means its tier)
Decorated Pentagon = Army Commander
Rounded Square with Pentagonal icon = Commander
Rounded Square = Civilian Unit that can be attacked (Scout)
Circle = Civilian Unit that can't be attacked (Missionary, Explorer)

 

[Racington]

This is fantastic, thank you. So basically, the Army commander get's the decorated pentagon, and the air and fleet commanders get the rounded square.