This coming Sunday is Judica, the beginning of Passiontide. All instances of the Gloria Patri are omitted and the images and crosses are veiled after the Gospel lesson. In a sanctuary with many images and crosses and few or no Servers, it may be more practical to veil all but the central two or three images before the service. Directly after the Gospel lesson the veils are placed, lowered, or raised (depending on what is being veiled) in silence.
My altar guild (a woman and her husband) really enjoyed rigging up the veil for our central portrait of Christ Blessing - it is raised by pulling a rope at the rear of the reredos. In my experience, people love these sorts of ceremonies: ones that teach about the faith in visible, almost visceral ways. During the Distribution many in my congregation gaze up at that central portrait: now it will be hidden for two weeks. And then when the veil is lowered at the Vigil as the bells ring and the Greater Gloria is sung – the joy of resurrection!
While over-explaining any ceremony can actually rob it of its teaching power, if this is your first year veiling the images you might include a bulletin or verbal announcement before the service along these lines:
As the Gospel words say, "Jesus hid himself and went out of the temple." The crosses and images of Jesus in the sanctuary are now veiled. As our mouths and ears have been fasting from Alleluia for all of Lent, now our eyes fast as well - we will not look upon these signs of faith and joy until the Easter Vigil.