For proper operation, check that the units of measurement in the scene are in mm:
Customize - Units setup - System unit setup - mm
The carpet material is made using the Displacement card (make sure that Displacement is enabled in your scene settings).

5 carpet sizes in the scene:
-310*400 cm.
-260*350 cm.
-210*300 cm.
-190*290 cm.
-160*230 cm.

https://royaldesign.com/eu/norlander-wool-rug 

More carpets: http://3dsky.org/collection/shared/5321350