Now, I'm not sure why this would have happened, but, make sure you have this option checked.
1. Go to User CP in top left
2. Under "Settings & Options" click on "Edit Options"
3. Scroll down to "Visible Post Elements" and make sure you have a check by "Show Image"
4. Don't forget to go down and "Save Changes" if you had to change something
This is the only thing I can think of that would be specific to this site. Hope it helps!