General alternatives:
* Representatives
* Envoys
* Ambassadors
* Commissioners
* Deputies
* Agents
* Representatives
* Appointees
* Plenipotentiaries (for those with full power to act)
More specific alternatives:
* Delegates (for those attending a conference or meeting)
* Representatives (for those representing a group or organization)
* Emissaries (for those sent on a special mission)
* Mandatories (for those given a specific mandate)
* Consuls (for those representing a country's interests in a foreign country)
* Spokespersons (for those speaking on behalf of a group or organization)
Informal alternatives:
* Reps
* Guys (used when referring to a group of delegates)
The best alternative will depend on the specific situation and the intended meaning.