Okh, I don't think that javadch wants to imports models, but rather he wants to store additional data. [;)]

javadch, you could store your data in the description property of a piece of furniture which is not displayed in the user interface at the moment. Or if you want to organize your data differently, you could use setVisualProperty / getVisualProperty methods in Home class to store and retrieve a map with furniture as key and some serializable data as value.
If you want something better, you'll have to to create a derived version of Sweet Home 3D something more complicate than programming a plug-in, but then you'll have the choice through customized controllers to override what you want.

See also this thread