Re: "I'd like to use an album in Photos as the basis for Wallpaper in MacOS 26"
"But I can only seem to add individual photos one at a time."
For MacOS Tahoe 26: Apple support's online article : Customize the wallpaper on your Mac - Apple Support
Eg: says: "Add custom wallpaper
- Go to the System Settings app
on your Mac. - Click Wallpaper
in the sidebar. (You may need to scroll down.) - Scroll down to Your Photos, click the Add Photo button, then do any of the following:
- Add a photo from your Photos library: Click Choose from Photos, then select a photo.
- Add an image file: Click Choose File, select a file, then click Open. You can also drag an image from your desktop or a folder onto the thumbnail at the top of Wallpaper settings.
- Add an album or folder from the Photos app: Select an album or folder under Photo Sets.
- Add a folder from the Finder: Click Choose Folder, select a folder, then click Open.
- Tip: You can choose the size and position of your wallpaper image, shuffle images and more. See Wallpaper settings."