This tag should only be used in one of the following cases:
The original artist themselves created a video using their own illustration (e.g. post #6849506 and post #5598651)
Someone directly commissioned an artist to create the picture for their video (so they were granted permission to use it as a thumbnail, e.g. post #6766229)
Making-of videos in Youtube and bilibili always include the respective illustration as a thumbnail. However, these must not get this tag because it would dilute its utility and make it redundant.
