First, actual mock-up (small part of level constructed from tiles) would be much more interesting rather that just set of tiles.

Second, few random dots on tiles filled with base color (green for grass, brown for earth, red for lava) does not make recognized and unique textures. You need more details and colors - bumps on earth (light brown-brown-black), lines on grass (few sorts of green), blobs on lava (dark red, red, orange, yellow), etc.