To celebrate the Halloween holiday, you can now download the free Windows 10 Halloween theme through the Microsoft Store. The wallpaper pack is called “Pumpkin Season” and the description reads as follows: “It’s pumpkin time. They glow, they grin, and usher in the fun. Get 13 festive autumn images in this free Windows theme set..”
After downloading the wallpaper pack, go to Start > Settings > Personalization > Themes and click on the desired theme.