Lenticular sheets consist of lens grooves on one side with coating on the back for printing images. From the lenticular lens groove side, we can see a very thin line of the image on the other side of the lenticular sheet, and this image line's location is determined by the observer's view angle. If an image is printed at each lens interval, the observer will see different images when looking from different angles.
Flipping (or views changing) is always the first choice. Different images could be seen when the card is tilted or seen from different angles. You could combine 2-3 different images, e.g. put your product's image or marketing message in one frame and your company's name or logo in another or merge images together to create various kinds of "Special effects".
Special effectis a derivative of flipping. The rationale is basically the same but the images in different frames of "Special Effect" always have high correlation and similarity. The most popular choices include animation, zooming and morphing.