super lowpolymodel : carpet is just made with 2 faces and specific "mental ray hair&fur" effect.
This means at render time the parameters become renderable objects and form the threads of the carpet.
Hair and fur parameters still adjustable to your own needs.
Mental ray light settings are included.

(red teapot is just for showing the height of the hairs)

hair and fur wool carpet fuzzy frizzy woolcarpet rug woolrug highpole mental ray mentalray