Right after the priest enters the Doors after the Great Entrance, he wraps the veil around the censer, gives it a shake (at least that's how my priest does it) and then covers the Gifts with it and then censes the whole thing.
What's the reason for the wrapping of the veil around the censer?
Essentially, what arimethea said.
The Great Entrance, in origin, is simply nothing more than the transfer of the Gifts from the place of preparation, (originally a separate building) to the altar for the eucharistic rite. However, all manner of symbolism later became attached to it, with the procession being seen as representative of Christ's triumphal entry into Jerusalem, the taking of the bread from the deacon's elevated hands as the taking down of the Saviour's Body from the Cross, and the laying of the Gifts on the Holy Table as the burial of the Saviour in the tomb. The aer, at this point, takes on the role of the burial shroud of the Saviour, so it is censed before being placed over the Gifts, symbolising the spices with which the Saviour's body was honoured. One of the troparia said quietly by the priest at this time is, "The Noble Joseph, when he had taken down thy Most Pure Body from the tree, wrapped it in fine linen, and anointed it with spices, and laid it in a new tomb". This is why the Royal Doors and curtain are closed at this point, symbolising the sealing of the tomb, (for them to be later opened as a sign of the Resurrection, as the Holy Things are presented to the people).
Tangential, but somewhat pertinent, is that the aer was originally much larger than it is today, and was carried over the Gifts during the Great Entrance procession. When all of the symbolism of the passion and burial came to be attached to the entrance, the aer came to be decorated with more and more elaborate burial scenes of the Saviour, which is the origin of the plashchanitsa (epitaphios, for Greek speakers), and the Great Friday ceremonies surrounding it that we know today.
