Howdy jkuil,
In my experience, the "Cleanroom" places no requirements on anything other than the air.
Furniture, walls, gowning, etc. are means toward that end and do not typically have standards on their own.
That said, your processes within the cleanroom may have other requirements regarding contact surfaces, etc.
There are several companies that supply cleanroom furniture...this one popped up in a web search
http://www.cleanairproducts.com/product-category/furniture-accessories/
In my cleanrooms, we have standard wood tables, metal cabinets, particle board, etc. and have no issue with air quality. Again, the actions within the cleanroom and the needs of the product may dictate otherwise.