A sense of beauty will be more fully developed. Here lies the difficulty. Many pictures make their own independent appeal. Children may not fancy each picture they study. That is fine.
Opinions are welcome.
Over time some pictures will become favorites to be appreciated right up into adulthood. Only what is necessary to really enjoy his pictures, except in the case of students age 13 or older. For example, when looking at Fra Angelica's pictures it is helpful to know that he spent much of his life in the community of monks at San Marco. Likewise, Jean-Fran ois Millet's works are better appreciated by those who know that he led the hard life of a peasant. I have found a little story of Millet's childhood and a legend of the boyhood of Raphael which I read to my children at odd times.