Absolutely you can remove it completely or replace it with a standard .jpg/.gif or whatever your liking. It's a little large so to replace it with a standard .jpg can reduce the page load time.
You've probably already tried this, but did you clear your browser cache? If you choose your own html block that should absolutely replace the flash with an empty grey bordered box, which you can then fill with your own image.
on 6.1 .... I uploaded new images, after deleting original ones...and its ok for a while then the original ones show up again and mine get renamed to big08. big08....weird.