I just saw this tweak and thought I would share it with you all. It’s called ConversationPics. The tweak is FREE in Cydia. By the name you should be able to guess what it does. It adds your contact pictures in your messages. 

I personally found that this tweak crashed my messages app for some reason but that might be a bug in the first release. Hope we see that fix and maybe a toggle in setting to turn it off.