As I'm not very found of editable combo boxes and similar components, I preferred to add an auto completion feature inspired from this blog article. The list of suggested strings I implemented in Sweet Home 3D is automatically updated and saved with preferences, as and when new texts are entered in the text fields of furniture, room and label dialogs.
It's also possible to have a default list of localized texts, and at this time, I just set the values for room names with the autoCompletionStrings#RoomName key in DefaultUserPreferences.properties (the two other keys are autoCompletionStrings#HomePieceOfFurnitureName and autoCompletionStrings#LabelText).

I hope you'll like it. Please test it the last version committed in CVS before I create a public beta.