that cigarette butt is a very nice touch! I think your 4th image lacks definition, I assume its a variant that's supposed to be smoothed over by years of water/steps? It's missing a bit of the lovely high-freq details you have in the other screenshots. My impression is that that kind of wear happens over centuries, so you can perhaps make it feel more consistent by reducing the height contrast & increasing the roughness a tad. The render stands out quite noticeably as looking 'odd' - particularly against the other lovely renders.