One tip though: the category of each object is stored in the preferences.xml file.
You could edit this file with any text editor, and change the text between > and < in the lines starting by <entry key="furnitureCategory#, like: could become:
The problem is that it won't be easy to recognize each piece of furniture since they are identified by a number and not by their name (the name you gave to an imported object is defined in the entries with a key starting by furnitureName#).

Before doing any tests be sure to create a backup of your eTeks/SweetHome3D folder.