II. Advanced Dungeons & Dragons?
Since the first slideshow was released in August 1993, it's hard to find earlier screenshots. Since the French always were something special for Bethesda, it seems like only french magazines featured screenshots before the slideshow was released. Three of them can be categorized as "may 20"-shots because they have no interface.
The first shot shows a typical illustration of Lord Bel or another Demon from Dungeons and Dragons.
The next screenshot shows another famous D&D creature that doesn't appear in the retail version: A Beholder. This creature is mentioned in more than half of the .inf files of the retail version.
The last screenshot shows an early version of the lich, that looks very different from the retail version.
Around this time (May/June 1993), a man named Nicholas Vargish applied for a job at Bethesda and got a little studio tour. Julian Lefay showed him the current version of Arena and in September '93 Nicholas made an usenet post about it. Nicholas wrote that Arena had reflections in puddles and crashed very often. In a second post, he mentioned very nice weather effects. In an email, he explained to me that he had to code a rotating cube as test for the job, but then he decided not to try to join the company.