Can you describe the history of the Sai Baba portrait that was given to Madhavrao and Kakasaheb Dixit at Mirikar's house?

Certainly. The portrait of Sai Baba that appeared before Kakasaheb Dixit had a special history. As Chapter 51 explains, this was a photograph that Baba's devoted disciple, Megha, used to worship with great reverence, viewing it as Lord Shankar himself. The glass on the portrait had broken, so it was sent from Shirdi with Balasaheb to Nagar for repairs. After being fixed, it was kept covered in Mirikar's drawing room, as if waiting for Dixit's arrival. It was then unveiled and entrusted to Madhavrao Deshpande to accompany him and Dixit on their journey to Shirdi.