There is a limitation of data types that can be passed in RPC arguments. You can’t send meshes (such as Mesh objects of Unity) directly through RPCs. Instead, you can assign an ID to each mesh or combined appearance and pass the ID (or a set of IDs) from the owner to replicas. A replica then picks up an appropriate mesh based on the received ID to apply it.
There are several ways to pass the ID, but the use of room member property is recommended when the appearance of the player avatar is concerned. Define a custom property (such as "avatarId") and set an ID as the value of that property. Replicas can change meshes when they are created and when a property change event is triggered.