How do I get wallpapers I saved in Pictures in my Admin user account in to my guest user account?

Thanks in advance.

copy and paste the image into the public folder as admin, once in there... login as guest and you can use it at its location, or move it somewhere more appropiate for your taste.

Copy and paste, or move, your images from the Pictures folder under your Administrator account to the Public Pictures folder which is located at %Public%\Pictures (simply copy and paste that address into the address bar in Windows Explorer and press Enter, it'll take you right to it).