I find this really interesting. Not just because of the style you used, but more because of the way you laid each element out on the poster. For example, I noticed that the rebels are facing the left of the poster and the Empire's armies and leaders are facing the right.
I also find it interesting that all the rebels have a determined look that they generally don't show in the films - even the horned creatures we see in The Empire Strikes Back.
I love everything I see that you do. If I had one comment to make as something to think about, a lot of your compositions have the characters facing to the left which works great standing on their own, but I think it would be nice to see some more variations design wise. I like this one in particular because, while it does follow that formula, it breaks it up a bit with Vader and the walkers facing the other way.