Emphasis

Emphasis

Emphasis by Contrast

Igreeny. "DeviantART: Where ART Meets Application!" DeviantART: Where ART Meets Application! DeviantART, 2012. Web. 26 Nov. 2012. <http://www.deviantart.com/?offset=96>.

One way to achieve emphasis in an image is by creating contrast. In the image above, the viewer's eyes immediately go towards the bright colors in the eyes because the contrast in color there is greater than the contrast of the colors in the rest of the image. 

Emphasis by Isolation

Emphasis by Placement

Aniline. "Digifox-Illustration." Deviantart.com. DeviantART, 2004. Web. 27 Nov. 2012. <http://browse.deviantart.com/?q=digital+illustration&offset=24#/d2qjeb>.
In the image above, the artist creates emphasis by placing the focal point, the girl's face,  higher up in the image rather than in the center.