More general:
* Representation
* Signification
* Symbolism
* Metaphor
* Allegory
* Emblem
* Figure
* Icon
More specific:
* Code (if referring to a system of symbols)
* Abstraction (if referring to a simplified or idealized representation)
* Iconography (if referring to the study of symbols and their meaning)
* Semiotics (if referring to the study of signs and symbols)
The best word to use will depend on the specific context and the intended meaning.