By default, Gmail tries to protect your email from spammers by blocking images in emails until you tell it to show them. That's nice and all, but it's a bit annoying when you want to see images from your contacts. Today Gmail changes that.
Now, instead of blocking all images by default until you click on the Display images below or Always display images from X links, Gmail will display images by default from your contacts (right now, contacts is defined by anyone who you've emailed at least twice, though that number is subject to change). It's a small but nice update, especially if you've grown tired of manually enabling images from contacts time and again.
On the other hand, if you don't like seeing images from a particular person or as your default, you can disable image display for individual senders or everyone, too. Here's how:
[C] lick "Don't display from now on" under the "Show details" link of an email from them with images. To disable images from everybody, select "Ask before displaying external content" under "External content" on the general Settings tab.
Good to know.
Now displaying images in messages from your contacts [Official Gmail Blog]