The Spanish civilization needs a rework in AoE II: DE, its representation is the poorest of all civilizations and needs some aesthetic changes.
First of all, the wonder: it cannot be that the wonder of the Spanish is an Almohad military tower, considering the enormous amount of architectural marvels built by the Spaniards, such as the cathedral of Burgos, the cathedral of León, the Gothic cathedral of Salamanca, the Alcázar of Segovia or the Casa de las Conchas, but personally I propose the Palacio del Infantado, a spectacular Gothic palace that in its original appearance had pinnacles on its upper part and Gothic windows on the facade.
Original appearance of the Palacio del Infantado:
Another thing very badly represented is the musical theme of the Spanish civilization, it shouldn’t be flamenco, since it’s 18th century music, a musical theme based on the medieval music of Spain should be used, like these examples of the 15th century:
-Propiñán de Melyor: https://www.youtube.com/watch?v=1Nd2GEXXsWU
-La más graciosa serrana: https://www.youtube.com/watch?v=QZBxSVDFpSA
Another aspect that should be modified is the architecture used by Spanish civilization, it makes no sense to use the same architecture as the Franks and the Britons. They should use Mediterranean architecture like the Italians and the Portuguese, but there should be a rework to the Mediterranean architecture since the current is nothing more than a modification of the Middle Eastern architecture. They have examples of medieval Mediterranean architecture in places like Santillana del Mar or Segovia. They can also use the architecture of Italian cities such as Venice and Siena. For the mill model they can use the windmills of La Mancha.
Finally I think it would be convenient to do some modifications to the El Cid campaign, such as using the Spanish in all scenarios, since you are supposed to be El Cid’s army regardless of which side you are allied with, all the Moorish armies represented by Berbers and Saracens, not Turks, and all Christian armies represented by Spanish. Other notable change would be to add a new type of forest, the Mediterranean forest; with characteristic trees such as the olive , the Mediterranean cypress, the stone pine, the sweet chestnut and the holm oak; to be used in the campaigns that take place in Spain, Italy and other Mediterranean places.