There is a long debate over who the "Us" is in Gen 1:26. Some people think that it refers to a divine council of gods, and is the remnant of an earlier polytheism in Israelite history, or even perhaps, a borrowing of creation texts, like Enuma elish, that assume polytheism. Others believe that this divine council is made up of God and His angels. Still others have argued that it refers only to God and He is speaking with what has been called the "royal we" supposedly used by kings in their address.
I think the last idea has been largely dismissed. I know of no "royal we" in Biblical Hebrew, and such an interpretation is likely a case of projecting the way we use the first person plural pronoun to refer to ourselves, as in "We are not amused."
The idea that this refers to a group of gods or angels is also not convincing, and I'll tell you why. In light of the fact that Genesis 1 is framed in terms of a cosmic temple (as many scholars suggest: Levenson, “The Temple and
the World,” 275–98; Walton, “Equilibrium,” 295; Weinfeld, “Sabbath, Temple,” 501–12; Kearney, “Creation and Liturgy,” 375–87; Wenham, “Sanctuary
Symbolism,” 403; and Arnold, Genesis,
48. Creation and temple are clearly linked in other creation texts within the
Bible as well (Giere, Glimpse of Day One,
65–66); also see Chapter 3 in my book, Revisiting the Days of Genesis), the image terminology, that is most certainly linked to the temple imagery, can help us see that man is meant to function as an image for God, not a group of gods, nor angels along with God.
Images do not represent a group of gods. Each god has its own image, and it certainly does not represent a deity and lesser beings along with him. It represents the rule of one particular god over a particular area in which that idol resides (beginning at the temple and moving outward within a particular sphere of influence). Here, the temple is the entire cosmos. God is sovereign over everything. There is no deity to share His domain, and that would not be represented by an image, but multiple images if more than one deity were being represented.
Now, one could argue that there are multiple humans being made for each deity, although angels would not be getting an image, so I think that such an interpretation can be dismissed. But the problem with saying that multiple humans are made for each deity is that the point the context is making is that this single God has accomplished victory over the cosmos and man is made to be His image. Hence, even if you were to have multiple humans made here, they all still function as His image, not separate images for individual deities.
Hence, I think the idea that this refers to a divine council of actual gods can be dismissed by the contextual referents.
This leaves us with two options.
(1) The plural here is meant to function as an ironic point that the author seeks to make about God, i.e., that He is the divine council all by Himself. He makes up His own mind and decides by Himself to create. He gains victory and rules by Himself, without the help or council of other deities. This does fit the context well.
(2) God is a plurality within Himself (i.e., there is more than one Person within the Godhead). Christians would then see this as a reference to the Trinity, even though it would be in masked form in the OT.
Scholars don't like the second option, and there are a lot of reasons for that, mostly having to do with presuppositions about what God reveals in the OT, or what the people believe about Him (since many scholars see the OT only as human ideas about God, not as necessarily revelation from God). If God has revealed Himself in the OT, and God was always Triune, then there is nothing to say that this could not be a reference to the Trinity (although God would not be placing the burden of trying to figure that out upon His people who are already struggling with polytheism and even faithfulness to Him as their sole God in the first place). However, if you believe that this text merely reflects what men believe, then the Trinity option isn't an option, simply because the author and his people would not have believed in the Trinity at this time. So presuppositions concerning the nature of the text (and those various presupps exist whether one thinks the text is inspired or not) play heavily into whether one would even consider the Trinity interpretation as an option. For evidence that Jews did see a plurality within the Godhead, one might look to what seems to be confusion over the possibility of different beings or attributes participating in His deity as persons one sees in the Second Temple Period (e.g., wisdom/logos, angels, etc.).
However, as a Christian, I don't think one has to believe either/or. God often has dual points to make in a text. Perhaps, He means to communicate both ideas: that He, as a single deity, not a group of deities makes up the divine council, and such is literally possible because He is more than One Person and can thus make up a divine council by Himself.
It's possible to see this as polemical to ancient Near Eastern creation accounts, where the council of the gods must convene and agree to create and make decisions over the cosmos. Hence, the idea of the divine council is certainly one that is at home in the ancient Near Eastern world, but what the text does with it is not at all. This would have been a shocking text to everyone who read it. A single deity is the council Himself? Such a new concept seeks to exalt God above the other gods by not only saying that He is the only one, but that He is of a different nature than the others. He is not just one deity plucked out of the pantheon in exclusion to the others, but His very being is different. He rules differently. This God is not like the other gods. In fact, in the Genesis text, there are no other gods at all. There is no room for them. There is one temple with humanity functioning as the one image/idol of the One deity. No other gods can fit in here.
So I think the "Us" in Genesis 1:26, and perhaps also then the subsequent uses in Genesis of the 2p plural (3:22 and 11:7--to my knowledge, I believe, it only occurs here and one other time in the Hebrew Bible in Isa 6:8), packs quite a theological punch within it, as it may exist to tell us something amazing about God, and perhaps, the text of Scripture itself.