See my response to There4. In Genesis 1, referring to one God, he is written in the ancient Hebrew as Elohim. (Plural). And yet tthe same people writing in other texts throughout the centuries have made it absolutely clear that God is the one supreme God and there is no other to be worshiped. And yet they did believe in angels and other heavenly beings.
So we when go to Genesis 2, written at a much earlier time for the obvious purpose to explain why things are the way they are, the "we" and "us" could refer to the all powerful, all encompassing God, or it could refer to God accompanied by that heavenly host. And no, I am not aware of another time that the same form of reference was used; however that ancient manuscript is a fragment of a very few manuscripts that have survived since that earliest record of the Hebrew/Jewish people. No doubt much more was written that didn't survive or we might have more examples of that manner of speech.
your response in the other post listing words that seem to be singular and end in -im is very nice but not on point. the noun's number follows the verb. so when there is a word like elohim which can be both singular or plural, simply look at the verb associated with it. in fact, mayim, water, though it is a singular concept is actually a plural word in construction as evidenced by the verbs associated with the use. you can look that up. rachamim is a singular concept but the verb (as in gen 43:30) or the adjective (isaiah 54:7) connected to it shows its plural structure; interestingly, the plural sense isn't of discrete number but of volume (eg. rachamim rabim -- great mercies). to then decide that the number is an indicator of some sociological limitation is to impose your understanding of their psychology on them. that's fine if that's what you want to do, but it is no more valid (probably less so) than simply following the verb and expecting that they said exactly what they meant. so when elohim is connected to a singular verb, it is a singular noun.
When the word elohim is associated with the plural verb (as in 1:26 and chapt 11), you can either see that there is a plural speaking (and thus the noun is a plural) or that the singular verb is speaking to a group outside of himself.
The issue in genesis and the creation is the plural VERB na'ase (let US make man). there, you can decide any of the following:
1. the writer was a believer in either polytheism or a compound monotheism
1a. the text is speaking of a multiple of objects though only a singular god
2. the text speaks in the unprecedented royal we
3. the writer used whatever word he had handy and we are looking too deeply in
4. the writer used the word intentionally to convey a deeper message or point to an external object of the speech included in the action.
you had opted for #2 by invoking the royal we. then you shifted to the heavenly hosts (1a).
judaism consistently understands #4.