My Designs of the Star Wars Characters in Episode 4: A New Hope sans Chewie.
Vader- I wanted him to look less like an opera villain.
Stormtrooper- I wanted them scary, like the elite troops of the Empire. Instead of 'oh look Stormtroopers' more of a 'holy bleeping bleep Stormtroopers! RUN!'
Luke- I decided to go with a suit ala Dune for moisture farmers. It would mark Luke as a country bumpkin even in Tattooine but Luke rebels as much as he can by not wearing the full face mask and growing out his hair to a shaggy length.
Ben Kenobi- A warrior in hiding is still a warrior. I wanted to make him still look formidable but older. He hangs out in ports like Mos Isley so he'd need to look tough
Han- Not really much of a change. Just gave him a blood-stripe on his jacket too.