For episode VI I found this...
The Empire Falls (tagline)
Return To A Galaxy... Far, Far Away (tagline)
Blue Harvest (1982) (USA) (fake working title)
Return of the Jedi (1983) (USA) (short title)
Revenge of the Jedi (1982) (USA) (working title)
Star Wars VI: Return of the Jedi (1997) (USA) (video box title)
Star Wars: Episode VI - Revenge of the Jedi (1983) (USA) (working title)
For Episode V: Empire Strikes Back I could find nothing else except two lame taglines
The Adventure Continues... (tagline)
The Star Wars saga continues(tagline)
For Episode IV the following...
The Star Wars
The Adventures of Star Killer - working title
Star Wars Episode IV: A New Hope - reissue title
Poster tags for Episode I:
Every generation has a legend. Every journey has a first step. Every saga has a beginning.
The saga begins Spring 1999
The Saga Begins May 19th
The Force Returns May 19th
One Truth, One Hate
Episode II Poster Tags:
A Jedi Shall Not Know Anger. Nor Hatred. Nor Love.
The Saga Continues.
Everything Good has a hidden Mask!
The Attack Begins May 16th