Photographs or clip art can be added as a background for your PowerPoint presentations. When you insert a picture or clip art as the background, PowerPoint will stretch it to cover the whole slide, if the object is small. This can often cause distortion to the graphic object and therefore some photos or graphics can be poor choices for backgrounds.
If the graphic object is small, it can be tiled over the slide. This means that the picture or clip art object will be placed repeatedly across the slide in rows to completely cover the slide.
Test your picture or clip art object to see which method works the best. The illustration above shows both methods.