Variety:
* Varied
* Multifaceted
* Heterogeneous
* Multiform
* Assorted
* Multifarious
* Eclectic
Difference:
* Disparate
* Differing
* Unalike
* Distinct
* Varied (also overlaps with "variety")
Inclusion:
* Inclusive
* Comprehensive
* Wide-ranging
* Broad
Specific to Cultures:
* Multicultural
* Ethnically diverse
* Pluricultural
Informal:
* Mixed bag
* All sorts
The best synonym to use will depend on the specific context of your writing.