Shilling is associated with Tonalism, a style that emphasises mood through a limited range of colours. He often painted trees and fields under overcast skies. In works like Autumn Stillness and Dutch Canal, he avoided sharp details. He used soft edges and subtle shifts in value to suggest form. His compositions frequently feature a single tree-lined road or a solitary bridge. He preferred the transition between seasons or the fading light of late afternoon.

Modern collectors value Shilling for his ability to create calm spaces. His etchings and paintings do not demand attention with loud colours. They offer a window into a still world. The simplicity of his subjects, such as a river bank or a row of trees, fits well with contemporary minimalist decor. His prints provide a sense of history without feeling dated. They work well in rooms intended for relaxation.