Saint Demetrius, Byzantine Steatite Icon

A larger detail of Saint Demetrius of Thessalonica, Byzantine Steatite Icon, 13th-14th Century. Kremlin, Moscow.

Icon of St. Demetrius of Salonica, Byzantium, 11th-14th centuries.
Source: Off The Beaten Trail: The Byzantine Masterpieces Of Russia’s Armoury, by Catherine Tsounis

Saint on horseback. Demetrius with a sword and a padded cuirass. Steatite (soapstone), Kremlin, Moscow.
Source: protostrator. Soapstone Warriors (military saints in byzantine carved icons)

Fig. 51. St Demetrios on horseback, 13th/14th-century steatite icon; Armoury of the Moscow Kremlin.
Source: Arms and Armour of the Warrior Saints (Medieval Mediterranean)

Referenced on pp. 8-9, MAA 89 Byzantine Armies 886-1118 by Ian Heath & Angus McBride:
Though Byzantine artists do not seem to have normally considered soldiers as suitable subjects they nevertheless drew, carved and painted endless numbers of military saints. This is one of them, St Demetrius, from an 11th-century ikon. He carries a large circular shield and wears quilted body-armour, probably an epilorikion. Note also his horse’s tied tail. A helmet would normally be worn, but saints are usually bareheaded in Byzantine art.

Referenced as figure 88 in Arms and armour of the crusading era, 1050-1350 by Nicolle, David. 1988 edition
88 Carved (steatite?) icon of St. Dimitri, Byzantine, 11-12 Cents.
(ex-Oruzhanaya Palace, USSR, present whereabouts unknown)
A number of features make the icon interesting. The armour is shown in an extremely stylized manner but may represent mail. The shield behind the Saint's left shoulder is very large. More significant, perhaps, is the fact that the horse is controlled with a curb bit while the rider adopts a straight-legged riding position. His saddle is, however, of the early low variety without the supporting cantle normally associated with the bent-legged position.