Planescape Campaign Setting concept art is from an ad in Pyramid magazine, number 7 (May/June 1994). Final box art is by Robh Ruppel. Perhaps the mock-up as well.
Interesting that the supporting graphics were retained, while the landscape is very different. While I love the final art choice, I have to say the concept art looks more exotic, in keeping with the setting.
I prefer the side panel design of the concept art. The final art’s logo is too big, dominates the panel.
Note the concept art’s title is Planescape: The Campaign. Bold.
I just noticed that the… unfinished bridge structure(?) element in the concept art… was retained in the final art. It’s very faint though. It’s much more visible in the ad art above.
See Also: Gamma World TSR placeholder cover