The word image is "Temunah" in Hebrew. Rambam in 1:3 explains that Temunah is an equivocal word sometimes meaning a physical image and the prooftext is this verse (to be exact, the same word in verse 15) but could also be used for a true notion grasped by the intellect and the prooftext is when Hashem says to Aron and Miriam about Moshe "Utemunas Hashem Yabit" and the Figure of God shall he look upon. Interestingly at the burning bush when Moshe hid his face because he was afraid to look at God, the Rabbis say that it is because Moshe did not let his first impressions take hold in his mind that he eventually was able to apprehend the true notion of God - Utemunas Hashem Yabit! Here again when the notion is God, Moshe sees fire . ( Of course the burning bush was a vision not real, being that a Mala'ach spoke to Moshe. Whenever Mala'ach is involved it is a prophetic vision - Moreh 2:42). Rambam tells us that the meaning of fire/darkness is something that is transparent. It is the equivalent of a molecule that when excited becomes fire and when left alone is darkness.(My understanding in Rambam 2:30 where Rambam uses an Aristoteleian idea of light, which I translated into contemporary parlance). The picture one gets is that the voice came out of a void. We already discussed in an earlier post that the Kol - voice, is an allegory for Divine intuition ( not exactly but close enough). In other words as the people were trying to assimilate the teachings about God that Moshe had taught them since his first introduction to them, further intensified over the last three days, they had a prophetic experience somewhat similar to Moshe, enough for each of them to understand what Moshe must be experiencing. The risk was enormous for they could easily succumb to anthropomorphism, being novices in metaphysical speculation. However as long as they were aware of Choshech, Onon Vearofel - the darkness, the clouds and the fog- that the transcendent God can only be apprehended as someone looking through a cloud or a fog, they were safe. The Onon, Choshech and Arofel (cloud,darkness and fog) are metaphors for how humans apprehend the Deity. When we try to develop an internal image of an abstract concept, we use our past experience as a basis. If I want to understand the radius of a circle I picture a circle in my mind. It is very difficult, in fact impossible, for us humans to apprehend a completely transcendental Being because there is nothing in our experience that we can hang our hat on. That difficulty is described metaphorically as a curtain (mossoch), as clouds, fog and darkness - (Moreh 3:9). Staying with the problem, accepting that we cannot cut through it, is crucial and necessary.
When we search for God we have to keep in mind that we will never really apprehend Him. We can only get a glimpse in our minds but whenever we think we know, we can be sure we are on the wrong path. That is why Anochi and Lo yhyeh Lecho are connected. It is only when one has a correct concept of Anochi , knows God from his deeds, he took us out of Mitzraym, not trying to comprehend His essence, that we can properly divest ourselves from idolatry.
That in my mind is one of the teachings the Torah is giving us by the way it retells Ma'amad Har Sinai. When we read these stories of Ma'amad Har Sinai the focus should be on the teaching not the historical facts. Rambam at the end of Moreh 1:5 where he discusses the meaning of seeing as it is told in the Torah e.g. Vayru'u es Elohei Ysroel (Shemos 24:10) that it does not mean a sensual perception but a mental apprehension, he ends "If however an individual of insufficient capacity should not wish to reach the rank to which we desire him to ascend (note the language! One has to wish not to reach!) and should he consider that all the words concerning this subject are indicative of sensual perception of created lights - be they angels or something else - why, there is no harm in him thinking this. Lets hope that we are not among those who wish to stay unenlightened. Good Shabbos.