We have these pictures that hang on the back side of our front closet, so every time the door shuts the pictures move. They are the type of frame with only one hanger right in the middle. I found the solution for me! They are called Soft Touch Gripper Pads, I believe Waxman is the brand, and I got mine at Wal-Mart for around $3. Just stick them to the back of the frame on the bottom corners or one in the middle.
What they do, because they are rubber and have little groves in them, is create almost a suction type of grip. I couldn’t believe it.
This may sound strange but I got these rubber heel grippers from the dollar store and just cut squares out and put them on the back of the frame. They are working great. You can obviously move the frame but they won’t move if a door slams. These are both cheap options to keep those frames straight! Yea!