Barry, another thing to consider from the model railroad bag of tricks is to run the dio/layout around the edges of the room rather than building it as a unitary piece on a 4x8 sheet. Granted, given the rather distinct "2-sides" nature of the battlefield, that might not work out well for Hoth! However, it might be an approach to consider for the revamp of Mos Eisley. I highly recommend Kalmbach's books on model railroad layouts - heck, any of their books, really, as well as their fine magazines Model Railroader and FineScale Modeller - for truly spectacular model-building, scenery-building, and dio/layout construction approaches.
Spook - WOW! Nice special effects work!