The predefined Cycles material nodes are made with Principled BSDF Shader. This shader is only available in Blender V2.79 or higher.
If you want to use previous versions of Blender you should create your own Cycles material nodes with the available textures in the zip file.
If you need more low-poly models you can use the DECIMATE modifier.
Photos were taken with a NIKON D300 and a professional studio flash light.
3D Models were created with Agisoft Photoscan (now Agisoft Metashape).
Models were remeshed and re-uved with ZBrush
Textures were created with Substance Designer.