The images are assigned a random class, to randomly position the images right and left, which is an attempt of me to make it look more like a folder (or whatever it's called in English).
To change this you need to take a look at the stylesheet. I do not know from the top of my head how I did it, but I guess you will find at least two different classes for the images. One foating the images left, and another floating the images to the right.
Bookmarks