When preparing your slides, finding images is often a long task. Free images are usually not high quality or require accreditation stamped on them or on your slides. Quality images are rarely free, and permission must be received – usually in the form of a paid license.
While you are building your slide deck, you may wish to experiment with different images until you have it just right. From most image sites, you can download a watermarked image to use privately or to show customers, testers, editors, and so on. Using a watermarked image is appropriate for building your slide deck, but in the final document, remember to spend the money for the correct license – and use unwatermarked images.