The Gmail team at Google announced in a Google+ post that the 'people widget' in Gmail would now display up to 3 recent photos that person has sent you. The photos will link back to the emails they were sent in.
The 'people widget' is the box on the upper-right side of an email that displays the name of the person in your email conversation. The widget offers different options pertaining to the person, including adding them to a Google+ circle or suggesting other people you may know through them.
About half of the comments to the Google+ post were praise to the Gmail team for providing this minor upgrade. The other half turned the comments section into a place to complain or beg for Gmail features they want or miss. Popular requests for the Gmail team included contact pictures with better resolution and an upgrade for Google tasks.
Personally, I would never have noticed the change if I had not seen this post. Along with a commenter to the post, I don't pay attention to the widgets. I had to dig into my Gmail settings to even see if it was turned on, and then had to search for someone who often sent me pictures. So it has a small window of usefulness, but it's nice to see that the people working on Gmail are concerned about the little things as well.