be a picture
To be very visually attractive or appealing. How gorgeous is their garden? It's just a picture at this time of year.
look a picture
To be very visually attractive or appealing. How gorgeous is their garden? It always looks a picture at this time of year.
be (or look) a picture
(of a person or thing) be beautiful.be/look a ˈpicture
look very beautiful or special: The park looks a picture in the summer.