MNPR offers 11 different substrates to choose from featuring various surface profiles:
The substrate data has been obtained from 2400dpi scans, whose profile was extracted using a shape-from-shading technique to acquire the UV inclinations and height map.
The raw data of the scans and lossless seamless textures can be found at NTU's data repository. A small tutorial on how to extract and acquire your own data can be found here.
Downloading the substrates from within MNPR is straightforward.
When downloading manually, make sure to extract the substrates under MNPR/textures.