I'm really loving the quality of the MDL Materials from the  NVIDIA VMaterials library. So far the only control you have over the appearance is the texture mapping method and scale. I wasn't able to access the map scale through the appearance, but you can use the texture mapping tab if you select the part with Part Selection mode.

Has anyone else given these a try? I'm having one issue where the MDL appearances switch to a bright pink color when I process the rendering. I was able to create these images with snapshots of the viewport in Accurate Mode. The MDL appearances also show as pink when in Preview Mode, but they appear normally when in Fast or Accurate mode. Here's the website I used to download the VMaterials: vMaterials | NVIDIA Developer