When did Orthodox bishops start wearing crowns?It it specifically menitiones that SS. James and John the Theologian wore the mitre (like the High Priest).
A mitre or a diadem
? (if I'm not mistaken you speak Greek: Διάδημα). Just like every official in the Empire, the Emperor (Empress), the aristocracy and the Church officials in their public appearances were "διαδεδεμένοι τὴν κεφαλὴν" ("had their heads diademed"; their diadem, or coronet was made of gold for the aristocracy and of diamonds for the Imperial family):Justinian's diadem
The coronet changed more during the Macedonian dynasty:Basil II's coronet
..and in the reign of Manuel I (Comneni dynasty) it resembles more the episcopal skouphos:Manuel I's Coronet
However, St. Symeon the new Theologian writes in the 11th Century for the Bishops:«ἀπερικαλύπτῳ κεφαλῇ οἱ τῆς Ἀνατολῆς ἱεράρχαι τήν ἱερουργίαν τελοῦσι» (PG 115, 716)
roughly, "the Eastern Bishops celebrate the Liturgy bare-headed"
:The famous mosaic of the Ravenna Basilica. Bishop Maximianus appears bare-headed
After the fall of Constantinople, for the first time, beginning with the Patriarch of Constantinople (the "ethnarch"
of the "Rum milliyet"
(Orthodox Nation) of the Empire) appears wearing the late Byzantine (Palaeologean) Imperial garments in 1621
(Patriarchy of Cyril Lucaris):Constantine Palaeologus' Imperial Garments