As you probably know there is no simple way to distort a MovieClip in Flash. The solution that I've found uses AS3. Special thanks to Thomas Pfeiffer and Ruben Swieringa. They share their experience with this problem.
Currently I'm working on an AIR application and in the header of it there is a nice gradient which has to be repeated by the x axis to fill the whole screen area. One way to do it is to use a really wide image, something like 2000px. The other way is to use a simple trick and repeat a small part with the gradient.
I'm absolutely sure that you've already met this problem. You know, these nice rounded buttons that are provided by the designer. They are really cool, but sometimes the label of the button is so long that you have to resize/scale the image. ActionScript3 provides simple way to solve this issue.