Hi pentaSTAR, welcome to the forum
I think this is quite a nice start you have here with this piece. One thing to be aware of when working on something with a lot of texture is to think of the
most significant forms when lighting. The large, overall shape of the structure will dominate how it is lit.
In this case the shape of the pillar is a tall rectangular prism, so each face (we can only see 2 here, the top and one side) will receive different levels of light. Depending of the positioning of your major lightsource either your wall will be brighter or the top will be brighter.
So with your piece, if the pillar was in an interior, such as a dungeon, the walls will be brighter and the tops almost total darkness. If it is outside, the sun overhead will light the top more. I've assumed the later and made a quick edit to show you what I mean:
So in summary: don't let the textures steal your focus when lighting!
Other points:
Grey subjects such as stone are excellent opportunities to play with tinted light. In my edit I added blues and greens to the shadows to imply bounced light from a blue sky and green field. The yellow tint you have present already works well in the brighter tones, where the yellow sunlight would be striking.
Always try pushing your highlights all the way up to near-white. This will help you to fight washed-out contrast and give vibrancy to your lit surfaces. Note the bright specular points on the corners of the stone in my edit. These parts are directly facing the assumed sun position.
Finally, regarding your pixels, be careful which colours are neighbouring which other colours. There are a lot of instances in your tiles where a very bright tone is directly against a very dark tone. This has the effect of implying an incredibly sharp edge - something that clashes with the rounded silhouettes of the stones themselves. Have a look at the stone work in my edit and try to find places in the tiling where I softened the edges. Though don't take what I've done as a finished state by any means, I did a very meagre pass on it
Also be careful with creating pixel noise when add rough texture. Spattering some pixels here-and-there can disrupt larger, clean pixel clusters and confuse the forms your are setting out to imply. With pixelling its often better to work in larger clusters rather than small ones where possible (single pixels of course being the smallest cluster possible!). I hope that makes sense.
