Wrong photo displaying for sender of iMessage on iPad - A Solution
I have written this in the hope this will help others who have had the same problem.
When I send iMessages to people, my girlfriend's photo displays instead of mine, from her Contacts card. At first I thought we must have set up our iMessages to use our shared @me.com account but checking the setting on my iPad showed my Yahoo account as my Apple ID and my ISP account as my send/receive.
Then I checked out the forums here and whilst I didn't see an answer, I found people suggesting checking Contacts and the iMessages settings for other problems relating to crossed wires of sorts. I had checked out the settings so checked out the Contact cards.
Neither of our Contact details matched re: email addresses (even the @me.com account was only against her record not mine) and only our landline matched phone-wise so I thought there was nothing there that could be causing it.
That's when I decided to do a full sweep of Settings.
When I got to General, I worked my way down the list and imagine my surprise when I found Siri of all things had her name down against it and not mine. Lo and Behold, when I changed this to my name and returned to iMessage, my photo now displayed against my replies.
So, if you have someone else's photo showing on your iMessage replies I strongly recommend you look at Settings > General > Siri first!
iPad (3rd gen) Wi-Fi + Cellular, iOS 6