Hey dude, Outstanding work! I REALLY like the first one. I love the way you have the warm and cold contrast and that neither is really limited to its own side.
. In my opinion though, the hills on the piece are too clean. you made a point of texturing the rest of that piece and breaking up clean lines but it looks like you blurred them which makes them stand out a bit too much. I DO like them though; I just think this piece would be better off as two pieces since there seems to be a split in style.
The third one is wicked though. I really like the composition of it and the horizontal smudge lines and that bit of shrubbery on the left which balances it out but doesn't steal focus. High five dude!
About the last piece. I like your attention to detail in it. It's actually making me want to work on one of my game ideas now.
Post more of your stuff. Right now.