Problem with cliff/rock Tiles

[Smaex]

Hi guys,
so i'm developing a top down game at the moment and i'll try to create tiles for the environment now. I like the artstyle for now but i struggle with the rock/cliff tiles. They just look boring and don't fit the style very much. I looked at tons of reference images but i don't get it. Has anyone a tip or a special technique for how to create stone-like environtment. I don't know how i should do it with such a simple and limited style to fit 

thank you all!

(don't know excactly how to post pictures directly so here's the imgur link, sorry )
http://imgur.com/a/PJlwk

[Sersch]

usually rocks need to have more texture, it is hard to imagine rocks with just a single plain color. Try to add some additional tones of the color and try to make contours of stones. If you looked up references you should get an idea of what i mean

[Smaex]

Thank you and I know what you mean. I just can't realise it in my own way. I came up with this and i really like it but it's just too close to the hyper light drifter reference i used. But i keep on trying to create something like this in my own style 

[eishiya]

If you look at photos of sheer/steep cliffs IRL, you'll find that they have layers, they're often staggered and have both gaps/dips and parts that stick out. There are often bits where earth can accumulate and plants grow. I think you'll have an easier time designing your tiles if you start with a simplification of the forms found in reality, rather than trying to apply a "rock texture" to your existing walls.

Edit: Check out the game Mandagon, which has very stylised cliffs. They're very blocky, and all the staggering is for playable areas, but perhaps it might give you some ideas. Of course, the rest of the game is stylised to match. You seem to be going for a more realistic look with your trees and grass than the cliffs.