The original text (i.e., the Hebrew) is indeed plural: our image. The common Christian interpretation is that this is a reference to the trinity; the common Jewish explanations are either (a) the use of “we” as royal plural is quite common in other ancient texts; and (b) God could have been speaking to the “heavenly host” (angels and such.)
To add to the confusion, one common Hebrew word for God is Elohim, which is a plural noun. The word usually means God, but could mean “gods.” Again, the explanations as above.
There are two views of the comments by MEBuckner on “other gods,” depending on who and when one thinks the texts were written.
(1) If you think that the earliest texts were written over time, by many authors, then there is an evolution in thought, in the concept of God. In the earliest texts, God is simply the most powerful of all gods, and very anthrophomorphic (He “walks” with Abraham, he appears in human form, he has fingers, hands, breathe, etc.). Over time, the concept evolved that the other “gods” don’t exist, and the anthropomorphism declines (or becomes purely poetic.)
(2) The term “gods” or “other gods” is used to mean “things worshipped as gods.” Ancient Hebrew is a fairly straightforward lanugage, and the writings are in a poetical form: “things worshipped as gods” was just too clumsy, and the audience hearing the words knew what was meant by “other gods.”
The concept of “executing judgement” on the gods of Egypt is just a poetic short-hand for a complex richness of concepts. Remember that Pharaoh was deemed a god of Egypt, and is seen in the bible as a symbol for cruelty and injustice. So “executing judgement” on the gods of Egypt includes the concept of showing the world that there is a Power for Right in the world, that is stronger than the powers of injustice.
Of course, it’s possible to accept both (1) and (2), they are not necessarily mutual excludable.
PS - This is textual analysis, not history, so please, don’t tell me “it never happened.” We’re analyzing poetry, not science.