This poster is based on the old boxing match promotional posters of the 30s and 40s, here advertising the big showdown between Obi-Wan Kenobi and the newly monickered Darth Vader.
UPDATE: Have now uploaded 2 follow up posters here [link]
and here [link]
2nd UPDATE: Thanks everyone for your feedback on this piece and for those of you who have requested prints. Unfortunately, due to copyright restrictions, I can't supply any of my Star Wars themed artwork as prints. Sorry.