They just slip from "New Pixel art" really fast ... and into obscurity )
Awesome pic indeed! Though underestimated again. Perhaps it is carma... 
Wow! I like the toy-like cartooniness of the machines and the lovely rendering of the ground, but as you said they're a little dissonant. There might be a simple fix like making the vehicles cast hard shadows or leave block-like tracks.
Great work!
Sorry if you have not understood what I wrote ... It's because I'm
Brazilian, and I'm using Google Translate.
I think we were going for more cartoonish looks for the tractors, check out other buildings from the game.
http://www.pixeljoint.com/pixelart/55960.htm
But I agree that they conflict with the ground a bit..
A masterpiece. Perfect textures, the earth, the hole and everything
where contain texture. I think one thing that has possibly
tractors were damaged, because they flee the theme of the work.
Seeing the work, I think there is a more targeted for the land, and
these things, you could have done some dirty effects on tractors.
The palette is impeccable, but the disadvantage is that the palette of tractors,
as mentioned above, could be a darker color, and you could have
explored further the palette. If it was to be like that (leaving
tractors highlighted), sorry. Assessing the work itself (which is what
I always do), from 0 to 10 is 9.3, for sure. Hugs. =)
Awesome!
I agree this could be even better with some dirt and scratches, worn edges and stuff. Also the trucks lower bodies and wheels should be in shadow, and the wheels are slightly out of perspective.
Moar mining and construction stuff please!