Wallpaper album still not working
The issue with wallpaper sourced from a Photos album is still not fixed in macOS 15 Sequoia. This is an ongoing issue since macOS 13 Ventura.
When selecting a Photos album as source in Wallpaper in random order (clicking on the leftmost photo with the two arrows shaped in a circle), the system will only show the first photo in the album or any photo you have clicked on before.
One workaround is to export photos in a folder on a volume (i.e. "Macintosh HD") and add it as a source in Wallpaper.