Surpik3D let you quickly generate several types of stitching automatically on your 3D model. Super easy to use thanks to its user interface. No Grasshopper skills required

Carbon Fiber, bump and medium gloss. RMTL with embedded diffuse and bump bitmaps. 

New version for rhino 5 here Auxpecker is an easy and free solution to get a pleasing realtime preview of objects directly on the viewport of Rhino

White hexagonal metallic grid. RMTL with embedded transparency and bump bitmaps.

Voronoize Any Brep or Mesh.

GRay - Generative Materials for V-Ray 2 and V-Ray 3 for Rhino

Got curious with the GH API when looking for a way to improve how I control and export animations from GH. For Rhino 6 due to some RhinoCommon deps.

A Wallpaper-group Symmetry Array Tool For Rhino