You can embed images using base64 in the image tag
for example,
<img alt="embedded images"
src="data:image/jpeg;base64,/9j/4AAQSkZJRgABAQEAYABgAAD...TRUNCATED....UUUUAFFFFABRRRQAUUUUAFFFFAH/9k=">
I use this method in my email signatures to ensure that the recipient Always sees my logo even if they have download images turned off.
There are plenty of online sites which allow you to convert an image into based64.
Just type Image to Base64 into Google.