Welp, I wanted to post in this thread when it was first opened, but then I forgot about it completely. I think I can contribute a little in discussing alternate architecture and painting.
This post of mine is very much inspired by the TL in my signature "And all Nations Shall Gather to It", which posits a world in which the first Crusades are more successful and result in a unified and more formidable Crusader State, allied to Byzantium and which eventually annexes Damascus and Homs. As of the current chapters, it is about to attempt a military conquest of Egypt.
So, in this world, I figured the alt-Crusader State would have a dynamic, if peculiar, architectural framework, in civil, military and religious buildings, not only due to the multicultural influx of Catholic European peoples that found it - notably Francien, "Provençals" (i.e. Occitans), Italians, Normans (both from France and southern Italy) and Bavarians - but also due to the heavy influence of the cultures attached to the Levantine universe: from Syrians to Arabs. These influences will be sometimes global, such as the absorption of the Gothic and Italian Romanesque styles in religious building, courtesy of the French, Lombard and Norman immigrants, but also regional or localized, such as the Armenians in northern Syria and in the area of the Sea of Galilee, the Byzantine one in the larger urban centers (such as Caesarea) and especially Arabic, which inspires the usage of gilded ornaments with
pseudo-kufic inscriptions, continuous arches and bleached stones.
Still in the topic of architecture, I'll point out a few examples I think would be useful to picture this complex aesthetic habitat for Medieval architecture. I apologize in advance for the image spam, but I believe they'll be useful right now.
Exhibit 1: the city of Homs/Emesa, ITTL, is occupied by French aristocrats, and they import the nascent Gothic style to construct the very first contemporary cathedral of the city. I figure that it could be similar to the Frankish cathedrals of Cyprus, which, albeit constructed in later date, are remarkable for the integration of the Gothic style to the local materials and tastes. As for military architecture, I suppose that a castle as formidable as the famous Krak des Chevaliers would not be out of place in Homs, considering that the city grew around a hill-top citadel.
Exhibit 2: the region around Lake Tiberias/Sea of Galilee, sees the arrival of a number of Armenian immigrants, and they grow to form a sizable minority in Palestine as a whole. So, there is a place where religious architecture is profoundly influenced by the Armenian style, with common use of blackened stones, detailed carvings and engravings,
bas-relief, and conical domes and it shows by the fact that they use
khachkars (memorial stelai) as tombstones and as road-markers.
Exhibit 3: in the region of Mediterranean Palestine, the local emporia will have a pronounced Occitan (
Southern Gothic) influence, as well as Italian one, and this intermingles with the extant Romano-Byzantine influence, with just a touch of Arabic styles. With time, it becomes something similar to what if we threw Cathar architecture in the midst of Oriental aesthetics. The Mirepois, Pamiers (tower pictured below) and Rieux cathedrals are the closest to what I have in mind, considering that they seem somewhat similar to the Moorish aesthetics.
Anyways, this are my two cents. Hope it was a good contribution to the thread. Sometime later, I'd like also to talk some about visual arts, such as frescoes and mosaics, which are very fitting with the time-frame and the place.