You must provide citations for images, just as you do for words, quotes, and ideas. Even if you find the image through Google, you must click on the image and go to the original source for the image (which won't be google -- it will be another website). To get to the original source, click on the image and then click "website for this image," usually on the upper right side of the screen. Here's an example of what happens when I want to cite this picture that I found by doing a google image search for "elephant":
Elephant next to a car. Digital image. The London Telegraph. 13 May 2008. Web. 9 June 2011. <telegraph.co.uk>.
Like most digital images, this photo has no official "title," so instead I described the image in a few words.
The elements are:
Title of image or your own description of the image. Digital Image. Title of the website where it was published (not google!). Date it was published (if you know it). Web (medium). Date that YOU saw it (today's date). Abbreviated URL.