Thanks guys, I'll try in my next endeavors more pixels using the forum (WIP)
In many ways the shading is very good; you have put admirable effort into making each stone look rough and irregular, but I think the shape of the bricks is a little too weird; they don't look like real masonry. Also, while each stone is shaded, the overall surfaces of the walls are flat. You can improve this, especially by studying lots of reference pictures.
Those rocks look strange, also the ones in the middle are pillowshaded.
Nice effect on those rocks.