Translation:There are two beautiful vases on the old furniture.
Cel mai vechi would be the oldest.
I'm not able however to explain why sometimes we put cel in there. I don't think it impacts the meaning if you say mobilierul vechi instead.
I'm not a native speaker but i think there is a pause when talking as if you were giving an explanation about which type of furniture you are talking about.
There are two beautiful vases on the furniture (pause) the old one.