All the materials, textures, models, sounds, etc. that are used in PlaneShift are created specifically for PlaneShift alone. Our license doesn't permit any art to be reused by any other project, and artists may only display what they have created through their portfolios. So using freely available models isn't an option at all. For one while it is a really easy route to get new content in pretty quickly, it eliminates a lot of the uniqueness of the PlaneShift world.