I suggest making sorta brushes in Rhino first. Like make a box with good UV mapping on it, make things like pre-mapped cylinders too. Then you make your level in sections. You could have sections of wall and crates etc all as furniture that you import as .3DS.
At the end of the day, Rhino is not ideal for level editing, very few modelling packages are. It is nurbs and being able to subtract geometry is great for level editing, but UV mapping afterwards is a nightmare for large levels - so if you must use rhino, work in in sections and keep track of them and their textures.
Van-B

Next time he runs past, GRAB HIM!