I'm assumming you really mean a slide show kind of animation?
If you just needs a swf that shows a slideshow..
If that is so, get the server to generate a list of the files in XML, your Flex application reads the XML list and reads the images/files and makes a slideshow. It may not be necessary to read all the files first - depends on your requirement.
If you need a swf that is a slideshow with embedded images..
You need to read the list of files, as above, but create an MXML file with the slideshow code and the images as embedded assets. Send that to the server and have a server-side script invoke the compiler. Bit of a rigmarole.
Mike Chambers has an interesting post on bmp handling:
Maybe I should have said there's no server to use here (AIR), and in any case, I'm just looking for a way to generate these "slide show" swfs using a crapload of bmps I have on my hard drive. (This doesn't even need to be done via a custom Flex app, even.)
Now, the animated swfs will end up embedded in a Flex/AIR app, but that I know how to do. I'm just a little stuck on how to most efficiently create a few hundred of these animations. Yeah, I could make 200 different versions of Flex swfs that just play an animation by hand, but that's work and somewhat crazy.
One possible solution might be to use the ant mxmlc task to generate these swfs using a single Flex app that "dynamically" loads the dependent bmps (or pngs) and plays an animation with them, but I don't know if there's a way to dynamically change the list of embedded images within the Flex app via input from ant at compile time.
That's why a free utility to do this would be so much easier...