This would involve a greater use of the illusionary aspect of the change.  A changeling cannot make itself into an inanimate object, and would have incredible difficulty assuming a nonorganic shape.  That being said, it is possible for a changeling to adopt the texture and coloration of inanimate objects in order to blend in to their surroundings, much like they do to blend in to a crowd.

As for partial transformations, they are possible but much more difficult to maintain than a full body change as they must be localized.