Add a gradient map onto shadow. (black to red).
than take a red brush, and brush around shadow. set it to soft light at 80%. Do this on a new layer of course.
duplicate your render, resize it, and go to Filter> blur. Change the opacity higher and make it blur so it turns into a nice background that matches up with Shadow. Put this behind your C4D.
ill post a nice signature tut later if I find some time.