Multimedia content needs to be properly cited just like a book or article. It's also important to understand when it's okay to re-use multimedia content. The following examples give some guidance:
Sometimes a multimedia image is copyrighted, but re-use qualifies as Fair Use. The concept of fair use means that there are some kinds of uses that do not require permission or payment. Typically, a "four-factor test" is applied to determine if fair use can be claimed or not when using copyrighted content.
Four Factor Test:
Website - Fair Use - weighing the Four Factors
Google - Copyright Statement
Providing Attribution - include as much of the following information: