The official website used a frame from the unaltered version of Star Wars. It’s cropped and weird looking, but it’s not from the GOUT or the Special Edition.
Here’s the Blu-ray with a luminance boost compared to the promotional image that I quickly regraded:
http://screenshotcomparison.com/comparison/156949
As you can see, the promo image has tons more detail, especially in Luke’s costume. It also looks like there’s different warping here, just like in the Reliance shots. I’d guess that this was from a potential new release, or as has been mentioned, a film still from the '97 version. It would be wonderful to have a scan of that just to get the missing detail for this shot.