Do not use Clip Art or other cartoonish line art when creating your PowerPoint presentations. Think about it. If the images are included in the software, it’s likely your audience has seen them already. Instead, choose professional-looking stock photos—or better, use images you’ve taken yourself. Your presentations will look much more professional as a result, and images of real people build a more emotional connection with the audience.
— Adapted from “Top 10 Slide Tips,” http://www.garrreynolds.com.