I went looking for its artist. The Web Gallery of Art attributes it to an unknown French artist, but it looked Flemish to me - another source attributes it to 'Andrieu d'Ippre, peintre de Paris' who left Amiens for Paris in 1444, and died in Mons in 1450. So arguably Netherlands rather than French.
I would love to know who the beheaded bishop is - St. Denis maybe? Which would militate for French. But the saint with the amazing fur trimmed hat, crystal ball, sword, and little terrier dog is REALLY who I'd like to identify.
This painting - a cross between a polyptych and an altarpiece - was executed for the Grande Chambre of the Parlement of Paris by a painter native of Flanders or the north of France. The frame, forming five lunettes, recalls the compartments of a polyptych. However, the surface of the painting is occupied by a single, united landscape showing the Paris of the time.The unknown painter is referred to as the Master of Dreux Budé.
The do mention Flanders, and I would guess that the beheaded bishop is St. Denis as well.
He may not be a saint at all, but the patron of the artist. Wealthy folks sometimes had painters put them into the scenes; they were paying for it, after all!