While each design theme has its own background colors, patterns or images, every slide in a PowerPoint presentation can modify a background by changing colors, gradient fills, or adding/subtracting graphics. The background is the area behind the text and graphics on a slide.
To customize the presentation’s background, click the Format Background button in the Customize group of the Design tab. The Format Background pane will appear to the right of the slide pane. When choosing a different color or gradient fill for the slide background, consider ensuring that a proper contrast between the font colors and the background make the presentation easy to read for your projected audience. A dark background might be appropriate with good lighting, but a dark room might necessitate using a light background color. The Transparency slide bar can mute the color by increasing the transparency percentage. A graphic can be inserted and strategically located to the side of the content placeholder by adjusting the Offset percentages.
After defining all background settings, click the Apply to All button to update all slides with the new background. The slide illustrated below has the Facet theme with a custom background and a graphic offset to appear to the left of the content placeholder.