Please accept this as constructive feedback! I marked some "technical" issues that should be easy to resolve.
Other than that, I can recommend one thing:
- enable material override (clay material on all objects)
- then set up some interesting lighting (e.g. maybe some warm sunlight? maybe contrast between different color temperatures from the sky and sun?)
- once you are happy with your lighting, disable the material override and work on your materials
You can also use the default tone mapping in Corona 9 which has the ACES OT operator on by default. It makes images look more "photographic" out of the box. :)