Try adjusting the background to become more oriented with the render. Some examples of this would be changing the blues to greens, adding some brushwork over Luigi, with general restrictions of course. Don't just cover him with a transparent C4D. Keep him in view without losing him. Blur and sharpen areas realistically. This will give you the illusion of depth that will dramatically enhance the signature. Experiment with centering Luigi, and the text. This will further point the focal attention to him. The text should be small, simple, and complement the overall style of the signature, which seems to be a simple vector-esque thing.
I do enjoy a good Luigi signature. Keep up the good work, and keep experimenting, you've good a good head start.