The Old European culture blog examines some interesting conjectures based upon Harappan seals.
One is that symbols for certain kinds of cities or areas within cities may have been shared between Harappans and the Egyptians according to a 2010 academic conference paper:
The crescent moon symbol is hypothesized to represent the "outer city" or places outside the walls of the city.
Another is that the Harappan city of Mohenjo Daro may have been known as the City of Cockerels (or perhaps Chicken City), based upon its recently domesticated chickens (even though it was founded 500 years before the earliest attested evidence of chicken domestication in the region). The symbol of two Roosters seems to be associated with the symbol following a symbol that seems to be associated with a large city. See, for example, the following seal found in Mohenjo Daro:
It also appears that the word for "Cock" or "Cockerel" in Sanskrit and probably also in the Dravidian languages and in many other Indo-European languages of West Eurasia may have a common origin in the Harappan substrate language. (I find that the theory that this word was borrowed from Dravidian which is often associated with the South Asian Neolithic Revolution ca. 2500 BCE unconvincing.)