After you customize the colors, it's time to add a background to the slide. In fact, all presentations have a background, but the default background is often white, making it appear as if there isn't a background. To change the background style, click the Background Styles button on the Design tab. Background styles are determined by the theme, so as the theme changes, so do the gallery choices.
And just as you can with themes, to apply background styles to some or all of the slides in your presentation, right-click the thumbnail and then click the option that you want. Place your pointer over any thumbnail for a live preview of how that background will look if you apply it to your slide.
Next, we'll see how we can use a picture for the background of a slide.
Tip By clicking Format Background at the bottom of the Background Styles gallery, you can give your slides a textured fabric or material look.