St. Nicholas is the patron saint of the Ruthenian Greek Catholic Church in the United States, and protector of our children. Traditionally, before bed the prior night, children would leave their shoes out and upon waking on December 6th they would find them filled with treats left by the saint from the night before. This is a custom observed by many East Slavs throughout the world.
In the illustration St. Nicholas is depicted feeding the poor while wearing the vestments of a Byzantine bishop, notably the omophorion, epigonation, and mitre. The mitre which is topped by a cross, and resembling an imperial crown, was not worn by bishops until after the fall of Constantinople; however, this is how the saint is traditionally depicted in Byzantine iconography.
(Artwork by Yosyf Bokshai, 1922; h/t MW)