The Shading Map material is primarily designed to let you get a "cel" look in 3D, like typical animated cartoons. You can use this shader for a 2D painted-in look rather than smoothly shaded 3D. The Ramp Shader, new in version 4.5, is a material designed to make it easier to create and control a cel or illustration-style look. The Shading Map material can be used for special effects. Its prior application for cel style shading is now taken over by the Ramp Shader.