Nice model you got there, you could do so much with it
There are few things why this image is not looking convincing:-
1> The clouds are implying that the Light source (SUN) is at the back of the scene. Thus, the reason as to why your lighting setup is not well suited.
2> Try browsing through some of the evening shot in web. You'll find that usually evenings are warm even tone and have long and soft shadows. Compared to which your scene is too saturated.
Anyway there are lot of improvements to be made but you should totally have a reference while working with a scene.
Perhaps your lighting setup would have more suited for a night environment.
Sorry for making changes on your image but you'll get an idea..