Cavalry model: are humans and horses bound?

Who can tell me how to replace only the character model on horseback,please?
image

I don’t know if it’s possible yet. I looked to modify a unit, I did not find. Moreover it is not yet possible to modify the icons of technology or unit and the textures of units and other. Or else I haven’t found.

But if you have any info I’m a taker.
thank you