Overall, it's a solid base. I would decrease saturation of the remote trees (to simulate haze). Generally lighting seems unconvincing to me. I believe due to the discrepancy between rendered light and the cutout trees that are lighted from another direction. Some Photoshop magic should do the trick. Possibly adding a bit of barrel distortion and chromatic aberrations?
Overall, it's a solid base. I would decrease saturation of the remote trees (to simulate haze). Generally lighting seems unconvincing to me. I believe due to the discrepancy between rendered light and the cutout trees that are lighted from another direction. Some Photoshop magic should do the trick. Possibly adding a bit of barrel distortion and chromatic aberrations?