Add different types of turrets.
I also see in the cutscene where the Star Destroyer explodes, features you blew up are back. Pls fix that.
There should also be a hangar on the underside of the Star Destroyer.
There should also be a tractor beam array (Imperial I) or communications array (Imperial II) on the command bridge.
Add texture to X-Wing and Tie Fighters.
Maybe add a Y-Wing as bonus?
Here is some reference.
http://fractalsponge.net/?p=166
Otherwise, good work! I love Star Wars.
P.S I destroyed the Star Destroyer!