What do the statues on Ilos represent?

Solution 1:

The statues on Ilos were visually ambiguous, presumably because it wasn't clear at the time how much of a part they would play in the trilogy. It's worth noting that while Ilos was formally a Prothean planet, the term "Prothean" is later discovered to be a name attributed to multiple races inducted into the Prothean empire during the previous cycle.

This is further confused by the statues on Ilos looking remarkably similar to the images given to Shepard by the Eden Prime beacon:

As we later find out in Mass Effect 3, these beacons are in fact Prothean, and Javik (if you have the From Ashes DLC) will berate you for using the beacon, seeing the warnings and then subsequently not acting on them.

If we, for a moment, assume that these statues are not an earlier representation of the Protheans, it is also possible that the statues on Ilos were created by a race from the cycle before the Protheans ruled the galaxy, more specifically the Inusannon or the Zeioph.

The Inusannon were known to have previously inhabited Ilos at some point during a cycle predating the Protheans, and the ruins of Inusannon civilisation later provided the Protheans with the knowledge necessary to develop mass effect technology.

The Zeioph are of note because they are known to have built elaborate crypts on the surface of the planet Armeni.