I just submitted box art for some GOG games which were rejected for reasons I'm not clear about. For example, I submitted this box art for
Goodbye Deponia which I got from GOG.com and received this rejection notice: "Art for digital entries should obtained from the digital storefront in question. So, in this case, GOG.com. The correct image is found from GOG search results or from third-party website gog.org. Notice the image dimension differences."

Thinking it was the landscape orientation that was the problem, I then submitted
this portrait-oriented artwork,
also from GOG.com, which got rejected as "Incorrect Box Art."
These images both came from GOG.com like the rejection notes say they should, so I don't understand why they're getting rejected.