When an image breaks for whatever reason, any token using it becomes inaccessible. This makes it impossible to select, edit, remove, or fix the token. If the image is only broken for the GM (Like if a player's browser still has it cached), then they are able to see things the GM can't. In some cases, this can essentially break a page, with the only solution being to remake it from scratch. This would be solved if tokens defaulted to a placeholder image (Even if it's fully transparent, which could be useful in other ways), or if there were some way to list all the tokens on a page