General:
* Outfits
* Attire
* Apparel
* Dress
* Clothing
* Garments
* Habits (for specific groups or professions)
More specific:
* Fancy dress (for parties or events)
* Disguises (for hiding identity)
* Uniforms (for specific groups or professions)
* Regalia (for ceremonial or formal occasions)
* Masks (for hiding the face)
* Props (for theatrical performances)
Informal:
* Get-ups
* Rigs
* Threads
The best synonym will depend on the specific situation and what you are trying to communicate.