Looks very... Minecraft-y. I like the tiles.
How does the terrain generator work? Are you laying down layers of materials? If so, you'll be missing some cool landscape features such as overhangs.
I actually made something similar over a year ago. The way I did it was to use 2D Perlin noise added to a vertical gradient; the values of the noise above a certain threshold were stone, and those below were air. Values in the middle would map to soil, so you get a nice band of soil between your air and rock. Once you have a basic terrain shape, you can decorate it by adding ores to random stone tiles, and grass to soil with air above.