I originally wrote about this painting here. It's significant for many reasons, partly because it's by Andrea Mantegna and painted in 1497. Its real name is Madonna in gloria e santi Giovanni Battista, Gregorio Magno, Benedetto e Girolamo or the Pala Trivulzio, as it was part of an altarpiece.
I thought about it again recently when I came across it on the Web site of the Restauratori e Restauri in Museo project, which is educating museum-goers on the history of various paintings through chronicling restoration work that has been done on them. It sounds fascinating, although I haven't been to see any of the displays as of yet. (I have been to all of the museums and seen the paintings before, though.)
You can read more about the history of the Mantegna, which is in the pinacoteca at the Castello Sforzesco, here. The main Web site also has information on the other three pieces currently included in the project: Michele da Verona's Crocefissione, which is in the Brera; the Ancona della Passione in the Museo Diocesano; and Gaetano Previati's Madonna degli Gigli, which is in the Galleria d'Arte Moderna di Milano.
Don't be scared away by the Italian names; most of the information on the Web site has been translated into English.