Reddit reviews Star Wars: Death Star Technical Companion

The old West End Games d6 system had two great source books.

The Death Star Technical Companion has a lot of interesting floorplans, and according to that, things like the Death Stars and Star Destroyers were basically built using the same modular rooms. They're not ready to use battlemaps or anything, but I remember there being a good deal of great layouts for things like crew living areas, detention center, etc.

http://www.amazon.com/Star-Wars-Death-Technical-Companion/dp/0874311209/ref=sr_1_1?ie=UTF8&qid=1452105488&sr=8-1&keywords=death+star+companion

There's also The Imperial Source book from WEG. I don't remember if there are a lot of deck/floor plans in it, but there is a TON of information on the Imperial military is organized.

http://www.amazon.com/Star-Wars-Imperial-Sourcebook-2nd/dp/0874312108/ref=sr_1_1?ie=UTF8&qid=1452105642&sr=8-1&keywords=west+ends+games+imperial

Obviously, neither will have compatible stat blocks for the new system, but if you can find paper backs of either for <$10, I'd say they were essential if your game is going to have a lot of Imperial Entanglements, and you want a solid source you can pull from without having to invent it all on the fly... which is also certainly an option!