General synonyms:
* Beauty
* Beautification
* Appearance-enhancing
* Decorative
* Surface
* Superficial
Synonyms related to specific types of cosmetics:
* Makeup (for face and body)
* Toiletries (for personal hygiene)
* Perfume (for scent)
* Hair care (for hair products)
More specific synonyms:
* Aesthetic (referring to the pleasing appearance)
* Embellishment (referring to the act of making something more attractive)
* Enhancement (referring to the process of improving something)
* Concealment (referring to the act of hiding imperfections)
* Treatment (referring to the use of products to improve skin or hair)
The best synonym for "cosmetic" will depend on the specific context in which you are using it.