As puckhead wrote, you can define the movement of still images manually using keyframes for scaling and the center position of each image (in the "Motion" tab of the viewer). This gives you full control, but it takes a minute to set it up to look right. The good news is that once you have found settings that work for an image, you can quickly copy and paste the motion attributes to other images - very useful if you have a lot of images that you wish to animate in the same way.