Do you want an unchanging number of images to slide in once from right to left? If so,then try this in KoolMoves:
1.) Put your images on a long filmstrip background,
2.) Select images and filmstrip background, then in top menus click on Shapes>Group,
3.) Position group at starting position,
4.) Click on "+" icon at bottom, and then click on "Add Copy of Frame"
5.) Position group at ending position.