It got a major boost during the Renaissance through the endowment of the Catholic Church who commissioned artists such as Michelangelo Buonarroti (most notably the Sistine Chapel) and Gianlorenzo Bernini to create some of the greatest masterpieces of all time.
The most famous image is no doubt Leonardo Da Vinci's The Last Supper.
Most Christian sacred art is allusive, or built around themes presumed familiar to the intended observer. For example, a depiction of a woman holding a baby or young child is almost certainly a 'Madonna and child', representing the Virgin Mary and the infant Jesus. Matthew, Mark, Luke, and John, the four New Testament authors of the life of Jesus, are commonly represented by, respectively, an angel, a lion, a bull, and an eagle.
In the 20th century, some Western artists completed works that were critical of Sacred art. Salvador Dali's The Crucifixion is a clear example.