The image shows St Amvrosy Optinskiy (Ambrose of Optina), one of the most beloved Russian Orthodox elders who lived from 1812-1891. Dostoevsky visited him several times, including after the death of his young son Alyosha, and it is believed that the author’s encounters with the revered Elder Amvrosy formed a major inspiration for his character Fr. Zosima in Brothers Karamazov. Here is a link to more information on the life and legacy of the saint: http://orthodoxwiki.org/Ambrose_of_Optina
A footnote to this passage in Brothers Karamazov describes it as “probably the master key to the philosophic interpretation, as well as the structure,” of the novel.
For more information on this topic, please link to this interesting blog article: http://payingattentiontothesky.com/2012/12/05/the-orthodox-understanding-of-the-relational-reality-of-personhood-ii-don-sheehan/