Let's consider the individual stones as it relates to the individual. Our lives are represented in those stones. We are magnificent pieces of art that God is slowly perfecting over our lifetimes. Psalm 139 reminds us that we are fearfully and wonderfully made.
Stones are worn down from weather, water, and human endeavors to perfect them. Just like the stones, we are worn down by the storms of life, not just physical storms, but by people and circumstances that we encounter. These often break us and find us in a place of wanting and needing God in our loves. As a person turns towards God, I imagine him/her as a stone brightening in color and getting softer in appearance.
As we learn and grow as Christians, we become even brighter and softer. I can't totally imagine what God's mosaic is going to look like, but mosaics here on earth point towards heaven and give us clues to His beauty. A beauty that is often better seen than talked about. A beauty that is in us and shines through us.
We, as individuals, are one small piece of an imaginably beautiful mosaic that God is continuously working on until the end of time.