MODO | 30 Free Matcaps
MatCaps, or "material captures" use the shading of a spherical image and applies it to the target surface by mapping corresponding normals from the captured surface onto that of the rendered surface. Many artists like to switch between several MatCaps while sculpting and modeling and I use MatCaps to get an alternate look at my model when working to look for dents or dings in the surface of the mesh. Below is a link to 30 custom MatCaps I've been using within MODO for my own work.
MatCaps are applied with the MatCap Shader in MODO, and can be added to the Shader Tree by simply selecting the MatCap Shader found under the Add Layer button- "Add Layer > Special> MatCap Shader".
You can download all 30 Matcaps here: Pushing points Matcaps