The nature of a material is mainly demonstrated through its highlights. This kind of vehicle wouldn't have a polished surface like a sports car and therefore requires less highlights, particularly strong ones. When adding this kind of detail you really need to think about the purpose of what you are painting (Fig.16).
I have added decals to show that it's been manufactured by a company for a squad or a team, which adds to the story and believability of the image. Again you need to think about the purpose of your vehicle when adding things like lights. In this case the lights needed to add to the aggressive nature of the image.
I find it helpful when presenting an image to add a silhouette of a man as it makes the scale more perceivable. I will often use subtle colors in the background and foreground as this adds to the sense of depth in the image. You can also use these colors to bring out some of the colors from your image (Fig.17). I also like to present the image with some alternative angles of the vehicle. This helps people understand the details and shape of the vehicle and helps better demonstrate its purpose (Fig.18).
Fig.19 shows the final image. You will see that I used a few graphic details to really finish everything off. This is to really sell the design of the image.