Moshe Ben-Chaim

Parshas Yisro concludes with the Ten Commandments, but then adds a few more laws, including the prohibition of making "with" God (intermediaries), any gods of silver, or gods of gold for ourselves. Why is this law of intermediaries separated from the Ten Commandments, the second command being a perfect place for its inclusion, that being not to accept idolatry? Couldn't the Torah economize and group both laws together? And what's the difference between these two laws, of rejecting other gods and not resorting to intermediaries?

Why is this new law of gods of silver and gold placed together with the Jews' request not to hear God "Himself", but that Moses should relay the law to the Jews? (The people thought they would die from hearing God directly)

It appears that this new law is unique, and not similar that God should group it with classic idolatry in the Ten Commandments. In the Ten Commandments, God prohibits the acceptance of "other" gods. However, this new law is not about other gods, but rather, not using silver or gold gods as a means of worshipping God Himself. This is a unique violation of intermediaries (see Ibn Ezra on Exod. 20:20), unlike the Ten Commandments that prohibits worshipping imagined deities; not God.

This explains why this new law is placed where it is. There, the people asked Moses to be the go-between between them and God. God told Moses the conditions of this relationship where Moses would relay God's words. God emphasized that He spoke "from the heavens." Meaning, there is no other deity except for God; the Jews heard (witnessed) Him directly, without an intermediary. God prohibits intermediaries precisely at this point, since the Jews now want Moses to be a go-between. This relationship carries with it the danger that they might gravitate too much towards the go-between, an intermediary. Therefore God tells Moses to convey to the Jews this new prohibition not to make gods of silver or gold "with Him." This phrase refers not to idolatry, but to intermediaries, precisely when the Jews sought an intermediary in Moses.

The Jews dreaded to continue hearing the voice God created, assuming they would die (Exod. 20:16). The asked Moses to be an intermediary (Deut. 5:24). Moses responds, saying that Revelation at Sinai was [not to kill them, but] to offer the nation the ability to wax greater, obtaining evidence of God and His laws so they would not sin in life (ibid 20:17). This dreadful sound, intended to be translated into a dread of sin. 

"And the people, stood from a distance, and Moses drew close to the darkness where God was (ibid 20:18)."  God then in structs Moses to highlight the fact that they have seen that God spoke to them from the heavens. Through Moses, God warns the Jews not to create silver gods "with Him", nor gold gods for themselves. It seems that God preferred to teach the prohibition of intermediaries when that impulse presented itself. And this is a wise method of instruction, for now the people would fully appreciate the necessity of this prohibition, amidst their request of Moses to be an intermediary.