Thanks allot guys !
Before I took out my childhood LEGO, I was extremely fascinated with all the castle creations. Lots of them used tan, dark tan, dark grey and sand green bricks in between the big grey walls, that's where I got the idea. I'm working mostly with a 90's color palette, so there isn't to much choiche.
Yes, the bricks beneath the bridge are meant to be rocks sticking out, and I think it looks not that good. Problem easily solved with some other shades of grey, wich I almost don't have.
Again, some lessons learned for next MOC's !