That’s a sweet idea – the way a sidewalk turns into a tiny glossy riverbed is a texture treasure. I’d start with a close‑up, paint the wet‑film grime by hand, then layer micro‑bump maps for the capillaries and cracks. Maybe throw in a tiny spot of “wrong” bump just to see if anyone notices – keeps the realism honest. Let me know when you’re ready to dive into the pixel‑world.