Different interpretations could be thought of for the placing of a mirror at the top of the Nowruz table.
One reason why there is a mirror on the Nowruz table could that is reflects facts.
By looking at a mirror, one finds his own image and tries to put down the look that she doesn’t like.
So the mirror could be the cause of a change for the New Year. After all what does it mean if all nature changes yet the human being does not look anew into his own life and try at its improvement?