This tutorial is going to be a very short one and not going into every detail of the progression of this image. Certain parts, such as the hair painting, will not be added into this tutorial. You will need a rendered image and Photoshop for this tutorial. You can probably use Paint Shop Pro or another graphics program, just adjust the tools. With that said, let's begin.
This is the rendered image straight out of Poser. I don't let Poser cast shadows in my images as I like to put those in myself and that will be touched on in this tutorial.
Step 1: Our first step in this process is the most important. Look at your image and imagine how you would see this hanging on your wall. What can be enhanced to make it look better? When I look at this, I see I need to give it a lil' more "oomph" and fix a few areas where shadows should be. First, I will start with the shadows. As you can see at the bottom part of this image, her panties and the background are standing out like a sore thumb. This is because I didn't allow Poser to cast shadows. So quickly, I will fix this so my attention is not brought to this area of the image anymore and I can focus on the parts that are supposed to be standing out.
Make a new layer above the image and grab your paintbrush tool. I'm not too specific on what type of brush I use, just whatever works with the image. For this one, I'll need a pretty good sized one and some black "paint". I slowly start painting in the black to cover up the areas that should be blackened and I'm going by the shadow casted on her legs to do this. After painting in the area, I will lower the opacity so that it's see through, but still shadowed. For this one, I lowered it to 85%.