In the (previous) legacy editor, you could delete images from the account and not just "remove" from the email. In this new editor, that feature seems to be unavailable.
Thank you for coming to the community with your suggestion! You are correct that you can not delete an image out of your account from within a campaign. However if you go to the 'Library' tab at the top of the page, you can select and delete images or documents from there. I can definitely pass on your suggestion to make deletion possible from within a campaign. If you have any other feedback or concerns, please feel free to share them here so we know where we can improve!