I don't like that style much but whatever, here some cnc:
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C4D: I like the idea that the c4ds build a cave.
Render: Good quality
Light: The render has this light on it (shining from the top), it's brownish/white but the blue light in the bg doesn't really fit it. There are also two light directions (top + side = no good).
I recommend you to place the blue light wholes on the spots where the render already has its natural blending. That means the blue light should be on his shoulders (left and right). That'll fix the colour and direction problem for the light sources.