Beads and the Babe
Of course this is wildly anachronistic and incongruous, considering that Christian prayer beads didn't exist for several hundred years after Christ's death.
But the pictures are interesting even so. For one thing, they often give us a good look at a string of beads and how it's put together. It's also clear that a lot of the painters are acquainted with real babies and how they love to play with things.
My irreverent sense of humor points out that I haven't yet seen one where the Infant is trying to hang beads over his mother's ear, or chew on them -- both of these being classic baby behavior! -- but of course the Son of God and Savior of the World is much too dignified to do anything like that! :)
From a practical point of view, when I was making my first historical rosaries, I found one of Ambrogio Fossano's Virgin and Child portraits gave me a very good idea of how much "slack" thread to include in the loop of beads.
We tend to assume in modern times that beads should be strung quite close with little thread showing, but clearly that's not the fashion for the 15th-century rosary shown here.
The extra thread makes it quite easy to slide the beads along one by one as each prayer is said, keeping track of one's place.
Here's my string for comparison. (Dyed stone and glass beads, silk thread, wooden end-bead):