What kind of an image should be used in this
animation?
That depends on the type of animation you are
using. I chose the clouds for my animation because I liked the effect produced
by the clouds. Regardless of what image you choose, make sure that it will look
good when animated. For example, the image you choose should include a similar
starting and ending feature. Compare the clouds on Frame 1 and Frame 500. Both
extremes of the clouds image share a large cloud that makes the transition from
Frame 500 back to Frame 1 look smooth. For several animations, I have used
pictures of a river, skyline, and more for the scrolling image effect;
therefore the image you select depends on the type of image and animation you
want.