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
These images both came from GOG.com like the rejection notes say they should, so I don't understand why they're getting rejected.