The phrase "pictorial field" refers to a visual environment or space that is filled with images or pictures. It means that there are numerous images present, creating a scene or setting that is filled with visual content. Full definition
The square pictorial field is divided into eleven horizontal bands of white, blue and peach acrylic paint. (tate.org.uk)
The square pictorial field is divided into fourteen horizontal bands of equal width, alternating in colour between white and peach, with pale blue used for the top one and bottom two bands. (tate.org.uk)
Bas distorts the conventional pictorial field by compressing the foreground and background, and by altering the perceived depth of the spaces in which his figures exist. (widewalls.ch)