Moving beyond the times of the New Testament (ca 30-125) we get into the earliest Christian writings:
Until the second century, expressions of popular piety, whether deriving from Jewish, Greco-Roman or other cultures, spontaneously came together in the Liturgy. It has already been noted, for example, that the Traditio Apostolica contains elements deriving from popular sources (The following examples can be traced to a popular context: the Benedictio fructuum (n. 32) in A. BOTTE (ed.) La Tradition apostolicque de saint Hippolyte. Essai de reconstruction, Aschendorff, Meunster Westfalen, ed. 1989, pp. 18, 78.).
The earliest saints (as we know them today, and as you know) were martyrs:
The cult of martyrs, which was of great importance for the local Churches, preserves traces of popular usages connected with the memory of the dead.
The note on this piece from the document: Some customs connected with the cult of the martyrs almost certainly derive from popular practices: lamps placed at their tombs; wreathes of flowers and leaves which lent a festive note to sacred places; fragrant unguents placed on the tombs of the martyrs; various objects, especially cloths called brandae, palliola, nomina touched to the tombs of the martyrs were regarded as precious, authentic relics; the custom of the refrigerium at the tombs of the martyrs.
Some thoughts and a significant note on veneration of the Blessed Mother:
Some of the earliest forms of veneration of the Blessed Virgin Mary* also reflect popular piety, among them the Sub tuum praesidium and the Marian iconography of the catacombs of St. Priscilla in Rome.
*The famous De Navitate Mariae (third century), also known as the Protoevangelium Icaobi and numerous accounts of the De dormitione Mariae of the second century, all bear witness to early Christian devotion to the Mother of God. According to scholars, these writings refer to many popular traditions which had a significant influence on the development of Marian devotion.
The CDWDS offers a cautious and optimistic thumbs up, when care is taken:
While always most vigilant with regard to interior conditions and the prerequisites for a dignified celebration of the sacred mysteries (cf. 1 Cor 11, 17-32), the Church has never hesitated in incorporating into the liturgical rites forms drawn from individual, domestic and community piety.
In this period Liturgy and popular piety, either conceptually or pastorally, did not oppose each other. Both concurred harmoniously in celebrating the one mystery of Christ, considered as a whole, and in sustaining the supernatural and moral life of the disciples of the Lord.
Of course, history is written by the victors. It may well be that certain excesses were curbed and we have only faint hints at their termination. Certainly, the New Testament informs us that the agape meal was once practiced, at least for one community. And it certainly no longer exists.
I think the useful lesson is that popular piety is tested before inclusion in the liturgy is approved. It occurs to me that Catholic traditionalists might counter that the modern Roman Rite underwent far less scrutiny than what the institution will insist upon for other pious practices. Be that as it is …
The full document, the Directory on Popular Piety and the Liturgy, is online at the Vatican site.