This is pure speculation, but in looking at this long seal from Mohenjo-daro [M-1271], and seal signs from Mesopotamia which we know the meaning of, it could just be that some of the Indus signs are also names of places or of particular cities.
Seals and tablets with inscriptions from the ancient Indus Valley Civilization.
A very interesting paper by Steffen Terp Laursen, an expert on Dilmun, or the civilization in Bahrain contemporaneous with the ancient Indus civilization, suggests that the round, so-called [Arabian] "Gulf seal", often found with Indus signs and creatures like the short-horned bull and standard, developed from ancient Indus seals and representatives moving westward. Later these types of seals followed their own development trajectory and their Indus iconography. The westward transmission of Indus Valley sealing technology: origin and development of the ‘Gulf Type’ seal and other
Four thousand years in the making, a free Indus script font package in scalable vector graphics for use in Word and other programs is now available. Over 1,800 signs represent the best Indus concordance by the longtime scholar Dr. Asko Parpola, engineered by the National Fund for Mohenjodaro.
"Following these criteria, at least one Harappan toponym can be isolated with a fair amount of confidence. Altogether 70 Indus insciptions have been recovered from Chanhujo-daro. Eleven of them contain the sign [shown], which is not known from any of the other thousands of Indus inscriptions found at other sites," writes Asko Parpola.
An article in The Verge discusses efforts by scientists at the Tata Institute of Fundamental Research and others to use algorithmic analysis to decipher the ancient Indus script.
"The Harappans had a goddess of war connected with the tiger, another large feline that was once native to the Indus Valley. On a cylinder seal from Kalibangan, a goddess in long skirt and plaited hair holds the hands of two warriors in the process of spearing each other."
There are some seals with clear Indus themes among Dept. of Near Eastern Antiquities collections at the Louvre in Paris, France, among them the Cylinder Seal of Ibni-Sharrum, described as "one of the most striking examples of the perfection attained by carvers in the Agade period [2350–2170 BCE].
One unicorn horn or two? Two leading Indus researchers, after years of thought and research, came to different conclusions.
"The earliest representation of a unicorn is found on seals and sealings from sites in the northern Indus region, dated to c. 2600 BCE." writes Jonathan Mark Kenoyer. "This motif is not reported from any other contemporaneous civilization and appears to be unique to the Indus region. The unicorn motif continued to be used throughout the greater Indus region for over 700 years and disappeared along with the Indus script and other diagnostic elements of Indus ideology and bureaucracy c.
The seal that the publicity emblem (above) for the film Mohenjo Daro is actually based on (below) offers the opportunity to look at one of the most unresolved issues in ancient Indus studies: what was the so-called one-horned unicorn, and where did it come from? Drs. Parpola and Kenoyer have two different perspectives. Asko Parpola writes "One broken round Indus seal from Mohenjodaro, M-417 (below), shows animal foreparts (protomes) arranged in a whorl.