Well… the Persians were Zoroastrian/Christian/minority off Jews and the Turks were…Turkick that invaded from the steppes to the north east. Both these civs + the Berbes (Tribal religions/Christians) were only converted to Islam after they were conquered by the rapid expansions of the Arabs/Saracens.
They share the same architecture and such because their cities were located in simmilar Biomes, thus they all used sand stone for their architecture. This is why I want an entirely unique architecture set for the Byzantines, because their Empire streached from Italy and Greace (30% of their empire), all the way into Anatolia,The Levant, the Sini dessert and across north Africa (+/- 70% of their empire). Thus they should have a Medi (Dark+Fudal), ME (Castle+Imp) Hybrid set but preferebly a set of their own that reflects the building architectures that was used in the majority of their empire.
Or this mod shown in this post will be perfect: Uniqe unit skins for each civ Please + Cucasus DLC
See this thread for examples of Byzantine buildings: Cacasus DLC + Byzantine Architecture.