Possible themes: The synthesis of tradition and modernity in his work, his role in religious art during a time of Western influence in Russia. How his works reflect the Orthodox tradition while incorporating European realism.
Check for any recent scholarship or updated information. Assuming there isn't much, as he's from the late 19th-early 20th century, but still, avoid outdated information. aleksei valerevich kovalskii updated
He also worked on iconostases and church decorations. The Church of St. Alexander Nevsky in Moscow. His transition from religious to historical paintings, like "Tsar Vasily IV Returns to Moscow After the Polish Retreat." His style's evolution from detailed, symbolic works to more naturalistic ones. Possible themes: The synthesis of tradition and modernity