Theft of thumbnails is becoming a bigger and bigger problem on GKC by the minute, it is having a domino effect on other creators making them think it is okay to steal thumbnails.
As long as your Doors game has a original thumbnail (with the exception of the creator giving you permission to use said thumbnail) you should be fine for the most part.
Another problem is reusing thumbnails without permission of the creators, a few months ago a user asked for a thumbnail and artists delivered. That user has since left the forums and it seems that they left GKC in total. Now their game & thumbnail has no protection.
@NoNoWahoo is right, other than that there’s not really much we can do (that I’m aware of). It’s kinda like the whole free builds thing in a way (not much we can do besides emailing Gimkit)
Idk if this counted as thumbnail theft. 1 idk if the original photo of doors was from the internet. 1: one of it added a tiny text to the original photo while the other didn’t. I couldn’t really say they are stealing thumbnails if the original photos are a public domain.