"Where is there evidence that there was prayers to saints or veneration of icons in the Apostolic age?"
The letters of +Ignatius and the Martyrdom Of +Polycarp. But frankly, B, that's neither here nor there. You Protestant types are often very successful in framing any discussion aboiut religion in terms of your innovative sola scriptura ideas. Prayers to saints are part of the Holy Tradition of The Church. That's where the practice comes from. Its also where the canon of the NT comes from. The KJV you read comes from neither the canon of the NT as established by The Church nor from Holy Tradition. If you choose to believe that if the KJV was good enough for God then its good enough for you, fine. If you choose to believe that the hierarchs who established the canon of the NT didn't pray to saints or believe in the Real Presence or preside at incense filled Divine Liturgies, that's fine too. If you believe the Holy Spirit guided our hierarchs only just far enough to determine the proper canon of the NT 1200 years before Luther and left them to paganism and damnation after that, cool. If you believe that the People of God were left to languish in spiritual darkness until the Reformers arrived, great. But you are historically and spiritually wrong and you make God out a gamesman, the author of evil and a liar.
One such icon is Christ Himself.
[Christ] is the image(*) of the invisible God, the firstborn of every creature:(Col 1:15)
The icon of Christ is what forms us and converts us:
whom he foreknew, he also predestinated to be made conformable to the image of his Son(Romans 8:29)
let us bear also the image of the heavenly.
(1 Corinthians 15:49)
we all beholding the glory of the Lord with open face, are transformed into the same image from glory to glory, as by the Spirit of the Lord.
(2 Corinthians 3:18)
putting on the new, him who is renewed unto knowledge, according to the image of him that created him.
(Colossians 3)
But wait! here is a crucifix:
before [the Galatians'] eyes Jesus Christ hath been set forth, crucified among you?(Galatians 3:1)
we preach Christ crucified, unto the Jews indeed a stumblingblock, and unto the Gentiles foolishness
(1 Corinthians 1:23)