Veiling of Images in Churches during Passiontide

As stated by the National Secretariat for the Liturgy of the Portuguese Episcopal Conference:

In the Roman Missal of St. Pius V, after the Mass on Saturday preceding the Sunday of the Passion was the heading: "Before the Vespers, cover up their crosses and images which are in the church. The crosses remain covered until the end of the worship of the Cross on Good Friday, and Images to the Hymn of the Angels (Glory to God in Heaven) on Holy Saturday. " See that it was the custom on the last two weeks of Lent, through which it wished to focus the attention of the faithful in the mystery of Christ's Passion. All that could cut into it, as were the images of Saints, was covered.

Dom Gueranger writes in "The Liturgical Year":

The presentiment of that awful hour [of the approach of our Lord's Passion] leads the afflicted mother to veil the image of her Jesus: the cross is hidden from the eyes of the faithful. The statues of the saints, too, are covered; for it is but just that, if the glory of the Master be eclipsed, the servant should not appear. The interpreters of the liturgy tell us that this ceremony of veiling the crucifix during Passiontide, expresses the humiliation to which our Saviour subjected Himself, of hiding Himself when the Jews threatened to stone Him, as is related in the Gospel of Passion Sunday. The Church begins this solemn rite with the Vespers of the Saturday before Passion Sunday. Thus it is that, in those years when the feast of our Lady’s Annunciation falls in Passion-week, the statue of Mary, the Mother of God, remains veiled, even on that very day when the Archangel greets her as being full of grace, and blessed among women.

Such a practice is highly encouraged even in modern Catholic Churches.  Traditionalist Catholics and Anglo-Catholics still observe the ancient practice of Passiontide. In fact, even religious icons, artwork, statues, and paintings in a person's own home are covered.

Quoting from "The Catholic Source Book":

Traditionally, the Fifth Sunday of Lent, one week before Palm Sunday, was called Passion Sunday or Judica Sunday after the first word of the Introit: "Judge me, O Lord..." (see Psalm 43). The veiling referred to the closing words of the Sunday's Gospel, "They picked up stones to throw at him, but Jesus hid himself, and went out of the temple" (John 8:59). The Lenten veil expressed the sorrow of the Church at this time.

There is also a particular unique exception that might apply some years when Passiontide falls during March, the month of St. Joseph. By way of exception, the Sacred Congregation of Rites decreed on May 14, 1879, that the images and statues of Saint Joseph may remain UNCOVERED when any part of Passiontide falls in the month of March, which is, of course, dedicated to his honor - even on Good Friday - but ONLY IF the said image(s) STAND OUTSIDE THE SANCTUARY (e.g., the nave). 

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