Many 3D artists would disagree with me, but I think that postwork is the most important part of any image. This is the Stage of the project that requires the most artistic skills.

Postwork is where I add the elements that I couldn't convincingly create in 3D software. The real challenge is to blend the elements with the rendered image in such a way that the observers never know that it wasn't part of the original image.
Postwork is also the stage of the project where mistakes can be fixed colors can be adjusted and emphasis using contrast and blurring can be addressed.
The image below shows all the postwork steps I added to this image for the final effect.