Hey, I noticed when you look at a picture someone posted as an attachment, go back to the previous page, and then try to backpage again, it just refreshes the post you were viewing; this is what happens to me:
Open a topic where someone has a picture as an attachment. Click on the picture to view it. Go back a page to where you just were. When you go back again, it refreshes the current page instead.
I am currently using Firefox as a web browser, not sure if that makes a difference or not.