Pick some C4D's that go with the flow. But since you don't have flow, and since your render is in the middle, I suggest picking something that goes diagonally left and right. Somewhat like an upside down triangle without the base type of shape. After putting them on, experiment with the blending options until you are satisfied. You may erase some parts of the C4D that go over the render. Of course, you can color the C4D to blend with the bg too. Hope this helped! =)