How could i have the user upload an image to a flash file?

you can use the filereference class to load a user file into flash:

var fileRef:FileReference= new FileReference(); 

button.addEventListener(MouseEvent.CLICK, onButtonClick);  

function onButtonClick(e:MouseEvent):void { 

fileRef.browse([new FileFilter("Images", "*.jpg;*.gif;*.png")]); 

fileRef.addEventListener(Event.SELECT, onFileSelected); 

}  

function onFileSelected(e:Event):void {

 fileRef.addEventListener(Event.COMPLETE, onFileLoaded); fileRef.load(); 

}  

function onFileLoaded(e:Event):void { 

var loader:Loader = new Loader(); loader.loadBytes(e.target.data); 

addChild(loader); 

}