Changing your user image from there won’t work.
Question: Since I have been using Mac OS X 10.7 Lion and later, I haven’t been able to control the login image of different users on the computer. Every time I change it, it reverts to something else.
Answer: This is strange, but Apple has introduced a feature that takes a while to figure out.
Your user picture, which you would expect to change from the System Preferences > Users & Groups preference pane, now works with the Address Book!
To make the appropriate change, you can actually open System Preferences > Users & Groups. Notice the place where it says Address Book Card: Open. This is precisely where your picture can be changed, and the only place where it will really stick.
Once you click on the Open button, double-click on the picture shown, and then press on the Choose button.
That Open button which solves everything.
This will make you browse your hard disk for the right picture. Adjust as you wish and hit the Set button. You’re done.
I know, it’s not exactly straightforward… but hey, that’s not my idea.