The Book of Blessings has some blessings that can take place in Mass, others that should not. For example, the “Blessing of Families and Members of Families” can take place in Mass. The “Blessing of Stations of the Cross” cannot.
A blessing that should not take place in Mass is in chapter 44 of the USA’s Book of Blessings:
“ORDER FOR THE BLESSING OF RELIGIOUS ARTICLES
INTRODUCTION
1442 The present order is used to bless medals, small crucifixes, statues or pictures that will be displayed elsewhere than in a church or chapel, scapulars, rosaries, and other articles used for religious devotions. …”
Another blessing not to take place in Mass: “Chapter 36 ORDER FOR THE BLESSING OF IMAGES FOR PUBLIC VENERATION BY THE FAITHFUL”. The Introduction includes:
“1259 Whenever a new sacred image is first exposed for public veneration by the faithful, particularly in a church, there should be a solemn blessing by use of the special rite given here; but the rite is not to be celebrated within Mass.”
Another blessing not to take place in Mass: “Chapter 71 ORDER FOR A BLESSING TO BE USED IN VARIOUS CIRCUMSTANCES”. Depending on what the paintings are of, this may be the most suitable blessing ceremony. The introduction includes:
“1985 The present order is in no sense meant to violate principles concerning blessings; it is not fitting to turn every object or situation into an occasion for celebrating a blessing (for example, every monument erected no matter what its theme, the installation of military weapons, frivolous events). Rather every celebration must be considered with balanced pastoral judgment, particularly when there is any foreseeable danger of shocking the faithful or other people.”
On the issue of blessing objects twice, here is an example:
“1150 When a church is dedicated or blessed, all the appointments that are already in place are considered to be blesed along with the church. But when the episcopal chair in the cathedral church and, in other churches, the presidential chair, the tabernacle, the lectern for proclamation of the word, or the confessional are newly installed or renovated, there is an opportunity to teach the faithful the importance of such appointments by means of the celebration of a blessing.” (Incidentally, the confessional should not be blessed in Mass, the tabernacle should be blessed in Mass, for the other objects blessing in Mass is optional.)
Reference: Book of Blessings, Liturgical Press, Minnesota, 1989, ISBN 0-8146-1875-8.