CCC 2132 The Christian veneration of images is not contrary to the first commandment which proscribes idols. Indeed, “the honor rendered to an image passes to its prototype,” and “whoever venerates an image venerates the person portrayed in it.”¹ The honor paid to sacred images is a “respectful veneration,” not the adoration due to God alone:
Religious worship is not directed to images in themselves, considered as mere things, but under their distinctive aspect as images leading us on to God incarnate. The movement toward the image does not terminate in it as image, but tends toward that whose image it is.²

1 St. Basil, De Spiritu Sancto 18, 45: PG 32, 149C; Council of Nicaea II: DS 601; cf. Council of Trent: DS 1821-1825; Vatican Council II: SC 126; LG 67.
2 St. Thomas Aquinas, STh II-II, 81, 3 ad 3.