I don’t know if you will include the Spanish or not in this game, but if that is the case, I have suggestions to represent them more faithfully than they did in the Age of Empires II: The Conquerors.
I don’t know how many ages there will be or which ones will be, but the English use Tudor architecture from the 15th century in the trailer, so at some age the Spanish should use Isabelline Gothic and Levantine Gothic architecture from the 15th century, here examples of these architectures:
Among the units of the 15th century we should find the “Guardias Viejas de Castilla”, the Spanish gendarmes; the knights of the military orders like the order of Santiago; the “jinetes”, a light cavalry that used javelins and adarga shields; the “almogávares”, a type of guerrilla skirmishers; and the heavy infantry equipped with plate harness and capacete helmets and armed with pole arms. The equipment was generally very similar to that of other neighboring nations such as France and Italy, the helmets mostly used were the armet and the sallet and the barbute to a lesser extent, the armors used were the plate harness, the chainmail and the gambeson; something that stood out was the unique kettle hat from Spain that extended to France and Burgundy, the capacete, the most widespread helmet among the infantry, precursor of the morion.
Heavy infrantry with capacetes and pole arms: