The Ouroboros often symbolizes self-reflexivity or cyclicality, especially in the sense of something constantly re-creating itself, the eternal return, and other things such as the phoenix which operate in cycles that begin anew as soon as they end. It can also represent the idea of primordial unity related to something existing in or persisting from the beginning with such force or qualities it cannot be extinguished.
A Complete Guide to Alternative Religious Symbols
The Solar cross is probably the oldest religious symbol in the world, appearing in Asian, American, European, and Indian religious art from the dawn of history. Composed of a equal armed cross within a circle, it represents the solar calendar- the movements of the sun, marked by the solstices. Sometimes the equinoxes are marked as well, giving an eight armed wheel. The swastika is also a form of Solar cross.