A little late on this one, but your change probably did work. I'll bet your browser was caching the old image. Clear and delete all cache and reload the page. Or better yet, use a "cache busting" strategy in your html such as:
<img alt="My company" src="/img/mysplash.jpg?ver=1.0" width="200" border="0"/>
And every time you change your image, be sure and increment the "?ver=1.0" part. This is what forces a browser to realize it can't use the old one.