This is very flattering to see a thread analyzing my art - though I cringe when I see these images because of how unfinished they are. I really really need to go back and finish it.
If your curious about my thought-process behind this, its pretty simple really. I tend to be super scared of saturated colors. Its a problem I've been dealing with for quite a while, so I've been really trying to study when it's appropriate to use them and how. Its really easy to end up with a entire image of super-saturated colors, and more beginner artists do this all the time. But it's just as easy to be too conservative and DEsaturate all your colors so they all play nice with eachother - but this results in a very drab image in the end.
Another thing you should watch out for is your process in general. If you spend too much time rendering each individual rock before moving on to the next, you lose the flow an composition you could have had by roughing out blobs of shape and color first.
I hope this helps... now I need to finish my tiles
Anyway, something I was really trying to focus on for these tiles is a warm-yellow lightsource. Everywhere where direct sunlight hits the tiles I made sure to tint them towards yellow and saturate them quite a bit. Wherever direct-light was not hitting a tile, I allowed the reflected light to define their colors a bit - which mostly consists of the blue sky and greenery around them. Separating the shading into these two parts helped give depth to the tiles beyond just their shape.
