You can download swf movies and edit them, extract graphics from them, etc. The only problem is that your ability to do this is severely hindered because when Flash outputs a file to swf format it flattens it, makes everything on one layer frame by frame.
i have in the past found an application that will take apart .swf files. i did a quick google search and couldn't find it again. i used it to extract passwords from flash files back in my hacking days.