While the photos are free, they also offer a premium ... WallpaperHub (to download official and unofficial Microsoft wallpapers), Pexels service, and more to download some best free wallpapers.
The undisputed king of free Zoom backgrounds, Pexels houses more than 450,000 photos and more than 50,000 videos in its Zoom section. With that many options, you have . . . well, options.