Annus Dierum Sanctorum Nequaquam vacuum abire patieris, sed dabis viaticum. Thou shalt not let him go away empty, but shalt give him for his way. Deuteronomy 15.13-14
The earliest depiction of Saint Barbara dates to the 7th century and is at the Church of Santa Maria Antiqua in Rome. It is one of the most fascinating churches of any time, but also one of the least known, but now much more successible thanks to Smarthistory, whose video about it you can watch here. Saint Barbara is visible to the right when they discuss the panel of the Maccabees.
Barbara and her tower were popular imagery in the later Middle Ages. The Church of Saint Barbara in Cairo preserved a 15th century icon and a 6th century wooden door not showing Barbara, but of some rarity (click next for a second image), both now in the Coptic Museum. You may compare the icon to a German woodcut of Saint Barbara, also of the 15th century.
The most stunning work of art depicting Saint Barbara is an evocatively unfinished painting by Jan van Eyck.
Nihil sub sole novum 