When a Revit family is replaced with a V-Ray Proxy or a Cosmos asset and its instance is associated with a Scatter, the V-Ray Proxy/Cosmos asset is the one that is scattered across the Scatter's Host object.
When a Revit family is replaced with a V-Ray Scene, the Scatter is ignored.
Currently, only the following family types can be selected as Scatter hosts: Floor, Wall, Roof Ceiling, Curtain System, Curtain Panels, Column, Ramp, Stair, Toposurface, Mass.
Currently, only the following family types can be selected as Scatter guests: Casework, Entourage, Furniture, Furniture Systems, Generic Models, Planting, Site, and Specialty Equipment. It is not allowed to add the V-Ray Decal family as a Scatter guest.