Formal:
* Shoulder straps: This is the most common and general synonym.
* Shoulder boards: Often used for military uniforms.
* Shoulder pieces: This is a more general term that can also refer to other decorative elements on the shoulder.
Informal:
* Shoulder wings (especially for military uniforms)
* Shoulder pads (can refer to clothing, especially for athletic wear)
* Shoulder ornaments (emphasizes the decorative function)
Other:
* Fringes (when epaulettes are specifically made of fringe)
* Braiding (when epaulettes are made of braiding)
The best synonym to use will depend on the specific situation and the level of formality required.