Okay. I spoke to the devs about this. The image tool was removed from signature creation due to how signatures work. Unlike adding an image inline to a message, which means the images are sent at attachments to the message, signatures work differently. Therefore, there's no way to insert images into signatures using the editor. What you can do, however, is use the code editor and insert an image via a static link...like from your website or an external site. Format the signature using text as a placeholder, then edit the signature and replace the placeholder text with a static link, like <img src="https://www.your-domain.com/img/companyLogo.png" />