From eiko; a likeness, i.e. (literally) statue, profile, or (figuratively) representation, resemblance -- image.
see GREEK eiko
a. Matthew 22:20; Mark 12:16; Luke 20:24; Romans 1:23; 1 Corinthians 15:49; Revelation 13:14; Revelation 14:9, 11; Revelation 15:2; Revelation 16:2; Revelation 19:20; Revelation 20:4; ἡ εἰκών τῶν πραγμάτων, the image of the things (namely, the heavenly things), in Hebrews 10:1, is opposed to ἡ σκιά, just as in Cicero, de off. 3, 17solida et expressa effigies is opposed toumbra; εἰκών τοῦ Θεοῦ is used of the moral likeness of renewed men to God, Colossians 3:10; εἰκών τοῦ υἱοῦ τοῦ Θεοῦ the image of the Son of God, into which true Christians are transformed, is likeness not only to the heavenly body (cf. 1 Corinthians 15:49; Philippians 3:21), but also to the most holy and blessed state of mind, which Christ possesses: Romans 8:29; 2 Corinthians 3:18.
b. metonymically, εἰκών τίνος, the image of one; one in whom the likeness of anyone is seen: εἰκών Θεοῦ is applied to man, on account of his power of command (see δόξα, III. 3 a. α.), 1 Corinthians 11:7; to Christ, on account of his divine nature and absolute moral excellence, Colossians 1:15; 2 Corinthians 4:4; (cf. Lightfoot and Meyer on Colossians, the passage cited).