You should start your own posting with this since I'm sure the Star War fans will get in on this but I will say don't forget the Nebulon-B frigate.
Actually the Nebulon-B frigate will be a Rebal ship but I could give the Empire a modified version of the Nebulon-B frigate, here is an updated version of the Imperial ship list,
Cargo:
Colony Ship (Escort carrier)
Space Miner (???)
Spore Ship (???)
Freighter (Merchant Vessel, used by all civs)
Transport (Landing Craft)
Constructer (???)
Huge:
Dreadnaught (Imperial II-class Star Destroyer)
Ranger (Venator-class Star Destroyer)
Excalibur (Arc Hammer)
Large:
Battleship (Victory-class Star Destroyer)
Avatar (Immobilizer 418 cruiser)
Padlin (Demolisher-type Star Destroyer)
Sledge Hammer (Acclamator II-class Star Destroyer)
Overlord (Nebulon-C frigate)
Medium:
Fire Hawk (Broadside-class cruiser kdb-1)
Battle Hammer (Tartan-class patrol cruiser)
Survey Ship ( Lambda-class shuttle )
Battle Axe (Carrack-class light cruiser)
Small:
Defender (Aggressive ReConnaissance-170 starfighter)
Scout (TIE Scout)
Cruiser (TIE Phantom)
Phoneix (TIE Defender)
Tiny:
Missle Boat (TIE Bomber)
Star Fury (TIE Fighter)
Covert (TIE Intercepter)
All I need are ideas for the Spore ship, Constructer and Space miner