Oh my God. Thank you for this. Please ignore any sarcasm/negativity; this is so helpful. I was just in the process of building almost this exact same thing for a client, but kept putting it off--partly because I couldn't believe it didn't already exist. Now it does! (For anyone wondering what it's good for, HTML e-mails are a requirement for any non-hacker oriented marketing endeavour and lots of companies are unable to use ie. MailChimp due to ie. security policy or just legacy CRMs.)
Please tell me that I (or ideally, a designer) will be able to save it at the "chopped up" stage so that the kind old ladies who work for my client will only have to click pictures to switch them and type in boxes to change that. Also, do you host the images too?