Here are some Church Fathers and their explanation of Genesis 1:26:

74 AD Epistle of Barnabas: “For the Scripture says concerning us, while He speaks to the Son, “Let Us make man after Our image, and after Our likeness” (Epistle of Barnabas, Chapter VI.—The Sufferings of Christ, and the New Covenant, Were Announced by the Prophets.)

150 AD Justin Martyr: Speaking of Jewish theologians Justin calls the Jewish teaching that God spoke to angels a hersey: “In saying, therefore, ‘as one of us, ‘[Moses] has declared that [there is a certain] number of persons associated with one another, and that they are at least two. For I would not say that the dogma of that heresy which is said to be among you (The Jews had their own heresies which supplied many things to the Christian heresies) is true, or that the teachers of it can prove that [God] spoke to angels, or that the human frame was the workmanship of angels. But this Offspring, which was truly brought forth from the Father, was with the Father before all the creatures.” (Dialogue of Justin Martyr, with Trypho, a Jew: Chapter LXII.—The Words “Let Us Make Man”)

180 AD Irenaeus “It was not angels, therefore, who made us, nor who formed us, neither had angels power to make an image of God, nor any one else, except the Word of the Lord, nor any Power remotely distant from the Father of all things. For God did not stand in need of these [beings], in order to the accomplishing of what He had Himself determined with Himself beforehand should be done, as if He did not possess His own hands. For with Him were always present the Word and Wisdom, the Son and the Spirit, by whom and in whom, freely and spontaneously, He made all things, to whom also He speaks, saying, “Let Us make man after Our image and likeness; ” [Gen. 1:26]” (Against Heresies 4:20:1).

200 AD Tertullian: “If the number of the Trinity also offends you, as if it were not connected in the simple Unity, I ask you how it is possible for a Being who is merely and absolutely One and Singular, to speak in plural phrase, saying, “Let us make man in our own image, and after our own likeness; ” whereas He ought to have said, “Let me make man in my own image, and after my own likeness,” as being a unique and singular Being? In the following passage, however, “Behold the man is become as one of us,” He is either deceiving or amusing us in speaking plurally, if He is One only and singular. Or was it to the angels that He spoke, as the Jews interpret the passage, because these also acknowledge not the Son? Or was it because He was at once the Father, the Son, and the Spirit, that He spoke to Himself in plural terms, making Himself plural on that very account? Nay, it was because He had already His Son close at His side, as a second Person, His own Word, and a third Person also, the Spirit in the Word, that He purposely adopted the plural phrase, “Let us make; “and, “in our image; “and, “become as one of us.” (Tertullian, Against Praxeas, Chapter XII. Other Quotations from Holy Scripture Adduced in Proof of the Plurality of Persons in the Godhead.)

200 AD Tertullian: Tertullian rejects the idea that God was speaking to Angels because our head is the creator, not a creature: “Since then he is the image of the Creator (for He, when looking on Christ His Word, who was to become man, said, “Let us make man in our own image, after our likeness”), how can I possibly have another head but Him whose image I am? For if I am the image of the Creator there is no room in me for another head” (Tertullian, Book V, Elucidations, Chapter VIII.—Man the Image of the Creator, and Christ the Head of the Man.)

200 AD Tertullian: “In the first place, because all things were made by the Word of God, and without Him was nothing made. Now the flesh, too, had its existence from the Word of God, because of the principle, that here should be nothing without that Word. “Let us make man,” said He, before He created him, and added, “with our hand,” for the sake of his pre-eminence, that so he might not be compared with the rest of creation.” (Tertullian: On the Resurrection of the Flesh, Elucidations, Chapter V.—Some Considerations in Reply Eulogistic of the Flesh. It Was Created by God.)

Origen: “it was to Him that God said regarding the creation of man, “Let Us make man in Our image, after Our likeness.” (Origen Against Celsus, Book V, Chapter XXXVII)

Novatian: “For who does not acknowledge that the person of the Son is second after the Father, when he reads that it was said by the Father, consequently to the Son, “Let us make man in our image and our likeness; ” and that after this it was related, “And God made man, in the image of God made He him? “Or when he holds in his hands: “The Lord rained upon Sodom and Gomorrah fire and brimstone from the Lord from heaven? ” (A Treatise of Novatian Concerning the Trinity, Chapter XXVI. Argument.—Moreover, Against the Sabellians He Proves that the Father is One, the Son Another.)

Constitutions of the Holy Apostles: “the divine Scripture testifies that God said to Christ, His only-begotten, “Let us make man after our image, and after our likeness. And God made man: after the image of God made He him; male and female made He them.”(Constitutions of the Holy Apostles, Book V., VII)

Source: http://www.bible.ca/H-trinity.htm