Backgrounds are a great technique to improve the aesthetics and readability of PowerPoint slides because it is a design-based program. Themes in PowerPoint assist in selecting backgrounds by default, thus the default background is set automatically every time you change the theme. You can keep other parts of the theme while changing the default background because the theme comprises more than simply backgrounds.
The steps to apply backdrops in PowerPoint are outlined here.
Step 1: Select the Background Styles command from the Design ribbon's Background group.
Step 2: Choose the background style that best suits your needs.
Step 3: To change the backdrop of a given slide, right-click on it and choose "Apply to Selected Slides."
Step 4: The new backdrop has been applied to the selected slide(s).
If the visuals in the slide background are distracting you from the material, you can conceal them and use a plain background until you finish working on the content. To do so, click the "Hide Background Graphics" checkbox on the slide you want to hide.