Just need a little help.

Alright im making a Zombie Roleplay Survival Server. The script im using is CakeScriptG2 on the count of its easy to work with the Factions. So i want to make a Zombie faction, i already made it in the hl2rp.lua, but the problem im facing is the models. I know how to add a model for a faction but i want to make it so there are multiple models for the Zombie faction so not everyone who is a Zombie in the server looks the same. Does anyone know how i could do this?