The city in the background has too much black in it. Either change the blacks level to become light grey or loose the city altogether. Everything else looks cool to me. The trick is not be able to do a small mattepainting, the real trick is doing it at 4K, or even at FullHD.
Good effort there Powell, apart from black levels do check your perspective and edges and also it would be a good idea to degrain / denoise your references and original plate before you do the DMP work and when its final apply the noise / grain evenly to the whole DMP or just the layers in comp.