It's not just you.
https://forums.launchbox-app.com/topic/91606-cannot-add-images-to-existing-games-in-games-database/#comment-494887
https://forums.launchbox-app.com/topic/91593-problem-uploading-artwork/
When attempting to add new images to existing games in the Games Database online, the Changes Status shows a broken image being added to a "New Game". Unsurprisingly, this is then rejected by moderators.