Sophisticated means a very good thing, and to my opinion your contest opponents should start worry..
I saw unreferenced dummy objects - what are they for? why you need to keep them?
About scene object - see as an example the gallery oceanFloor (under folder Ocean) or the Garden (under Nature) - it gives you a whole 3D background, it may contain water or sand with topography, trees, etc. The scene/background object may have subparts but much of it is a picture, thus consuming less memory and less processing time in Alice.
When building a scene/background object (using any 3D creation application) for your game, the only reason I see to have subpart of the scene as an object is to reference it specifically from the program code, otherwise it should be part of the background 3D object texture.