My advice for you, specifically looking at your medieval things, it seems as if you like to over-complicate your designs, looking at your city wall engraving. Sometimes going with a simplistic design goes the farthest. Not to say you should make a wall out of just cobblestone, but when you do heavy engraving, and detailing on every part of a wall, things look cluttered, and almost tacky.
Also, on big buildings and cathedrals, don't be afraid to use different types of stone; you don't have to stick to stone brick alone. Sometimes cobblestone, regular stone, and even 43:8 (double half slab) blocks look nice too!
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