i cannot remember where i have seen this but i have a memory of a craggy rock cliff. i guess it was some sort of slate where you had all these layers protruding outwards making the surface look kind of like a pile of tiles.

this is what i have come up with so far. its a horizontal and vertical stretched voroin 4th neighbour pattern used for displace/bump. but it still looks very geometric. so i would like to know if you have tips for making this more irregular. maybe more bump nodes? or just some good surface colour settings?

thanks in advance
chris