'iconed' is formed from the modern English verb 'icon', which in turn comes from the noun 'icon' borrowed into English from Medieval Latin 'eicon' or Late Latin, ultimately from Greek 'eikōn' meaning 'image, likeness'.

'icon' entered English via Medieval Latin/Old French forms from Greek 'eikōn', and the verbal use (to icon) is a later, productive formation in modern English; 'iconed' is the regular past/past-participle form of that verb.

Initially the root 'eikōn' meant 'image' or 'likeness'; over time English developed the noun 'icon' for a pictorial symbol and then the verb sense 'to represent or mark with an icon'; 'iconed' retains this meaning of 'made into or marked with an icon.'