A little headache in Gmail is that embedded images don't show up by default. That actually makes sense, as that can be data-intensive. Until recently, there was no way to force images to always load. But Gmail recently updated so that you can tell it to always display images from a particular sender. Just look for the button you see highlighted above.
You can also clear the list of senders that will automatically show images. Just go to Menu>More>Settings>General Preferences>Clear "Show pictures" and you can reset the list.
- Tips and Guides