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The design is pretty unique. My suggestion is to improve the shading of the tank, if the tank is made of metals then the shading should have specular/highlights and higher contrast, try use blinn or phone as the base. Your must have an ambient light in the scene that makes everything look flat and un-interesting. try start with a basic three point light setup. Some textures seems stretched and not detail/sharp enough, you might want to pay attention to that as well.

I will improve the lighting and texture ,i just use two ambient light in the model top.
Sorry,i don't know where three point can do (a basic three point light setup)
Thank you very much