The tree of life connects the ground and our physical existence to the skies and the heavens. It unites all forms of life to mother earth and the universe. It is widely recognised and cited in many faiths and cultures including Christianity, Buddhism, Islam, Judaism, Hindu and Baha'i - all over the world, uniting all of humanity and the universe as a whole.
The Flower of Life is one of the most sacred of geometric symbols. It is a geometrical shape composed of multiple evenly-spaced, overlapping circles arranged in a flower like pattern with six fold symmetry like a hexagon.
Crescent Moon & Star Symbol, not truly Muslim in origin, almost everything I've read credits the Ottoman Empire for the adoption of this symbol however it is the most widely recognized, which is what I was going for with the religious symbols collection.