I love the look of this illustration. I have always enjoyed the homages to the classic recruitment posters. The layout is great. I agree with putting the Death Star from Jedi as the completed one might look a little off.
The only think I would suggest is maybe putting some lighter highlights (maybe not white as it would take away from the stormtroopers) in Vader's helmet. Adding highlights might help make his profile seem a little more fleshed out.
Other than that I think it's a great poster and would like to see more like these to come. Good job.