First of all, you may hear from people who agree with you, but you'll also hear from people who disagree with you. Please get used to this, since it happens a lot in life. You have come to a conclusion based on Scripture and you are seeking other people or references that verifies your conclusion as accurate. Does this mean you are going to discount any evidence to the contrary? That is not a very meaningful dialogue, then.
There shall be
enmity between the serpent and the woman, as well as between the
seed of the serpent and the
seed of the woman. Her
seed shall strike at the head, while the serpent's
seed shall strike at the heel. The previous verse (Genesis 3:14) describes the first part of the curse upon the serpent:
"On your belly shall you crawl, and dirt shall you eat all the days of your life". Let us look at the various messages found here, from the mythical to the spiritual.
Mythical
As the first chapters of Genesis explain the creation of the universe, it is expected there are parts that answered the ancient Hebrews' questions of "why is such-and-such the way it is?" So, why is it that snakes, which look very similar to reptiles with feet, have no feet and slither upon the ground as they do? Well, because the first serpent was a wicked creature that tempted the first humans to disobey God's command.
Physical
Snakes which crawl on their bellies bite at the heels of people, whereas people can step on the heads of snakes. Rather plain and simple, really.
Word Meaning
In another post you said the Hebrew word nachash translated as "serpent" also means "shining one". This makes sense to me, since the skin of many snakes is shimmery. Call to mind also 2 Corinthians 11:14, where Paul writes that Satan masquerades as an angel of light. An angel of light, a shining being, a shimmering being, not unlike the Hebrew name for a serpent.
Spiritual
If the serpent is seen to be the catalyst for sin -- Satan, the adversary of God, who pits human wills against God's will -- then we must examine what is said in a different way. The serpent's offspring bites at our heel, which can disable us but does not necessarily kill us. The woman's offspring, however, strikes at the head of the snake, killing it. Sin has the power to disable us, but we can overcome sin altogether, through a very specific offspring of the woman: Jesus Christ.
So then, we can see that, physically, Genesis 3:15 is stating that humans strike at the heads of serpents, whereas serpents for their part generally strike at our heels. But Genesis 3:15 also foreshadows the coming of Christ who will crush the serpent (Satan, the advocate of sin) under his foot,
even as Satan strikes at Christ's heel!