Congrtulations on getting Region 1 Season 5 Box Set DVD's. I know how the anticipation felt. I had to wait a while. Not as long as you did probably, but it was a wait nonetheless.
Anyway, Regarding the Gallery Stills on the first disc. They don't exist. It's just one more of the numerous Box Set screwups brought to you by MGM and whoever put the DVD art work together. Sad, I know. No Region 1 box set has the stills. Not to worry. As for the messups, Region 2 also has discrepancies and the like. The latest messup I heard and saw for Region 1's Season 5 box set DVD's is the picture opening for Meridian is actually the technology from the episode Sentinal.
In juxtapose (crud quality of special features and art work vs...) for the most part I am happy with the DVD picture quality of all the seasons.