As you can see in the pictures above, lighting can play an important role when giving a presentation. People in the back may not be able to see your facial expression and emotion because of bad lighting. In the picture on top, the speakers face is not visible from the back of the room. While there seemed to be plenty of possible overhead lighting, for some reason none of it was on.
In the picture below it, this is the room where I did my presentation.
One tip for all speakers is to arrive early, find out where you are going to stand and make sure that the lighting is turned on so that the audience can see you. I had plenty of lighting in my room and was able to turn off one light right above the screen and still have plenty of light for myself.
If you are going to be the most important part of the program, make sure that people can see you.