Why use the Creative Commons?
Using images in your presentations and course design is a great way to improve the message you are trying to deliver. It is important to remember that most images you find online will have some sort of copyright restriction on them.
The Creative Commons also includes other media eg: audio, video, text, data etc. Check the particular Creative Commons Licence for the item you wish to use - this will tell you what you are permitted to do, then attribute according to the guidelines.