Light is one of my most favourite things to play with when photomanipulating. It is a very useful thing that helps to bring mood to the image and sometimes can even play a role in giving more focus to your subject or whatever you want to highlight. I use it every time, however it's not always obvious, but it makes the difference.
Atmospheric light is particularly useful if you want to add detail without overloading your work with different objects. Because it allows you to create highlights and bring out the things you want to, while keeping the rest subtle. It also helps to blend everything in seamlessly and gives the image more depth.
I'm going to give out a few tips that help me in playing with this and getting some interesting results.
The trick in creating the mood and atmosphere with light is knowing the surroundings in your work and having an image of the light source. From there