You can now use fetch() to add your headers and then load the result into an <img>
:
const src="https://api.mywebsite.com/profiles/123/avatar";
const options = {
headers: {
'Some-Header': '...'
}
};
fetch(src, options)
.then(res => res.blob())
.then(blob => {
imgElement.src = URL.createObjectURL(blob);
});