Would you be able to share the code that is used in the email to display the image? In addition, a screenshot or copy of the HTML from gmail so we can understand how it's making it way into the mailbox itself would be helpful.
Hey Tim, you could try changing the subject line of the email and sending another test. I've seen Gmail "selectively" show some content and not others, and/or it'll also sometimes color your text purple, if it's something that's repeated from a previous email in the thread. This has happened most to me when Im testing an email and send myself more than one copy (so that there's a few similar copies in the same thread).