Here's how to view those images:
- Sign in to Gmail.
- Open the message.
- Click Display images below in the green box above your message. Or, if you'd like to always view images from a particular sender, click Always display images from sender@domain.com instead.
If you choose to always display images from a particular sender, you can disable this functionality at any time by following these steps:
- Sign in to Gmail.
- Open the message.
- Click show details at the top of the message pane.
- Click Don't display from now on.
At the moment, you can't set Gmail to display all images from any sender; you must do this on a per-contact basis.