https://developer.mozilla.org/en-US/docs/Web/HTML/Element/ma...
You will get a better response with a text only message.
Quite a few people do exactly that.
In my case the result is: Big red placeholder image and copyright text /unsubscribe link underneath it.
If you get a HTML template you can use mailchimp or exact target to put custom html to each subscriber / subset and do A/B tests. It takes more time up front, and limits what you can do (er outlook / gmail limits that) but if you get it right it will pay off down the line.
I assume there's a big empty table where the image would go and some text+links above and below the image.
They let you write HTML and CSS, test in the browser, and only at the last moment convert `p { text-color: #333 }` and `<p>..</p>` to `<p style="color: #333">`