Gmail will soon, by default, display images included in e-mails. Users will still have the option to disable this behavior, but since it’ll be the norm we can expect that eventually HTML e-mails will display pretty much as designed as soon as they’re opened.
The change does not, however, eliminate consequences for poor design. For example, a nearby Chamber of Commerce frequently embeds its entire message in an image. While more Gmail recipients should now begin to see the Chamber’s e-mail as designed, mobile users and the visually impaired will continue to have difficulty with its inflexible format.
The bottom line: Gmail’s change won’t magically make images accessible, so use them only to accent your e-mail – not to convey important information. That should always be communicated using text.