LINK TO IMAGE (I have no idea how to embed the image itself :C)

Hi, I started to make a pixel tileset with some rocks but it just doesn't look right and I can't even make the flat part to not look like crap :(

I collected lots of reference images but it just doesn't really help and I don't know how to fix it that's why I'm posting it here.

EDIT: There is my current version of this tileset

It's still not quite what I want and I still think the pattern looks ugly :C