There are a few good places and it depends if you are looking for high end or not.

Decoracion Actual in Cancun is great and have quite a showroom, mostly high end, our bedroom was $6,000 US there 3 years ago.

I am currently programming a web site for them and they are doing all of the furnishing for another client of mine in Puerto Aventuras. You can see the furnishing examples on that site http://portobelloclub.com

Another option is in Playa Del Carmen on the highway called Telebodega. Better prices and lower quality on furnshings, appliances are good prices and they have same day delivery.

There is a new furniture store on the highway in Cancun near the Mercedes dealer. Don't know the prices but heard they are high end stuff, some imports from italy.

Good Luck