|Provided you had no error messages, it will actually be showing the new image.
However, your own computer will have a cache and it is showing you what it knows your page looks like, rather what it actually looks like.
Hold down the Ctrl Key and click on refresh.
Hold down the Ctrl Key and the F5 key, in Internet Explorer, it will force your browser to reload the page.
And your new or replaced image will appear like magic.
Just like that!