Make it Scary

Use an image that is repulsive, scary, or unpleasant. Things that frighten or sicken us, even mildly, still hold a fascination for most of us. Get more mileage out of scary or ugly images by zooming in or making them larger to accentuate their features.

In the sidebar illustration, I'm not sure I'd want to take a business card with a lifesize roach (even a picture) crawling across it - ewwww! But you can't help but notice it. A cast shadow gives a 3D touch.