On one of our recent treks from Genzano to Nemi and back, in the Colli Albani outside of Rome (the somewhat overbuilt but still charming hills that glitter on the skyline in the evening), we managed to be in town when the kids of Genzano were doing their flower "paintings" on the streets. The kids did theirs a week ahead of the adult Genzano "infiorata" - or flowering. We were fascinated to watch the middle- to high-schoolers as they waited, not so patiently, for the flowers to arrive and for their turns to come to start putting the flower petals in place.
From what we could see, the designs were done through earlier school competitions. The theme was human rights, and one featured women's rights (against the veil, it seemed to us), using English. The adult version, to come a week later, was more tourist-oriented, and focused on Caravaggio.
What we didn't realize until we saw them do it, is that the flower designs are done almost solely with petals. There aren't any flowers that stay alive in this process. Colored flower seeds also are used to fill in certain places.
We hope you enjoy the kids' projects as much as we did watching them. And we encourage you to get out to one of the small towns that have these festivals (flowers and otherwise) with some frequency from spring through summer.