Chrome extension displays sender's picture in conversation threads to liven up GMail
Well, would you look at that! Someone put together a Google Chrome extension which does exactly that. If your sender has a picture attached to their Google profile, the extension adds it in below the reply/forward/etc. drop down.
And on the off chance that you can't remember who a sender is by their name alone, now you'll have a handy visual reminder. Unless, of course, they don't have a profile pic -- in which case you'll just see a light blue cartoony head. In that particular case, it probably won't be helpful unless you're communicating with Brainy Smurf.
Personally, I just enjoy a small image breaking up the monotony of text which I've grown accustomed to in my inbox.
One more thing: no RAM is used by this extension. Sweet.