Well initially for the Empire they'll have Star Destroyers (maybe including different classes), TIE Fighters, TIE Interceptors, TIE Bombers (possibly TIE Advanced and Slave I, can't really see the Lambda Shuttle fitting in).
For the Rebels they'll have: Corellian Corvettes, Medical Frigates, Transports, big Mon Calamari Cruisers, X Wings, Y Wings, A Wings, B Wings, Millenium Falcon
From the pictures there may even be different arrangements of fighters available.
Oh and somewhere down the line they'll release a £70 Super Star Destroyer for the real junkies.