param should work for you. If you got an error about missing bracket, you might be missing leading or trailing bracket. I know the code checks for it, since I wrote the %flash modification. I have tested on numerous blogs.
here is syntax for %flash param: %flash[url, width, height]
is location of .swf movie. If movie in theme 'images/header' folder, url can be just filename, or url can be full URL if .swf in different location.
is width of flash movie in pixels, the px suffix is optional.
is height of the flash movie in pixels, the px suffix is optional.
here is link to %flash article
. However, using %flash will apply to all pages, not just home page.
Good Luck with it!