One of my colleagues always uses our school colors in his presentations, and I think that is great. Also, make sure that the color scheme is used throughout the presentation. The most effective way to do this is by using the slide master. Make all your layout decisions on the slide master, and they will automatically be carried throughout the presentation. Use Clip Art - One of the easiest ways to make your presentation interesting is to use clip art.
Pictures draw attention to the important lecture points.
I know I can find a picture to suit any topic material I am teaching. Colorful pictures can really transform your course material into captivating presentations. By this I mean make it interactive. PowerPoint is a multimedia application. Use the effects, transitions, and interactivity that makes PowerPoint such a good program.