General Synonyms:
* Shop
* Store
* Establishment
* Retailer
* Emporium
* Specialty store
* Consignment shop
* Haberdashery (for clothing)
* Gallery (for art or crafts)
Synonyms emphasizing small size or exclusivity:
* Small shop
* Independent store
* Mom-and-pop shop
* Exclusive store
* Upscale store
* High-end shop
* Fashion house (for clothing)
Synonyms emphasizing specialization or niche:
* Specialty shop
* Concept store
* Boutique hotel (for hotels)
* Boutique law firm (for legal firms)
More informal synonyms:
* Shop
* Store
* Place
* Joint
The best synonym will depend on the specific context of your writing.