Ok. i love the colours, I can't teach you anything there. (others can, not me)
But there are some things keeping it between what you have now and something truly awesome.
Forgive my blunt paint skills:

1: That diamond does nothing to me but detract from the overall power this piece could have.
The combination of colours it's made of give is slightly different from anything else in the piece.
Maybe it has some narrative meaning. But i don't know that meaning and its glinting just distracts me.
I by myself am not that important but i like to believe i speak for more people when i say this.
2: As mentioned before. That building removes the mystery of the building before it.
Being totally in the middle i get the idea that the front building is of great importance. And then there is like this big brother photobombing it with its tallnes. You can solve this by removing the building. or make it less tall and multiples of them. I'd op for the first.
3: That bridge is horizontally perfect. Seems flat in comparison with all the vanishing lines in the piece.
It destroys the depth that some other vanishing lines try to build up. There are more of theses srtaight horizontals in the piece.
That is not per se a bad thing. Swords and Sworcery does awesome things with straight horizontal lines.
But in here the balance is off. You could remove the bridge or compose it of a diagonal line.
4: It sure seems like water to me. Regardless of light source.
Where these guys overall stature disappear in the moss, Their shadow just takes over following the same lines.
Because of this it looks like i can see through the moss...Moss is not transparent.
Writing this comment i noticed a lot of other things. But i want to conclude with that it could become a very very very cool piece of art.
Please continue.