well, as you'd do in JavaScript too, to "preload" images you can take advantage of the caching feature on client computers.

so what you basically do is load the images in the background (ie: somewhere invisible), so that when you later load them they will have been cached and will load instantly.


for such purpose you should probably proceed this way:
1) put all the image addresses in an array;
2) make a loop run through the addresses array and create a new movieclip to be used as container for each image and load the image within it;
3) by using the MovieClipLoader class (on which you can find all the necessary documentation in the Flash Help, by pressing F1), you can trigger an onLoadComplete method, which you will use to destroy the MC's once the images are loaded.

This way you cached the images.

Hope this helps!