As a matter of interest you can change an image in the html using css like this:
width:0;/* hide image*/
height:0;/* hide image*/
padding:61px 0 0 160px;/* background image width (160px) and height (61px) */
background:url(image2.png) no-repeat 0 0;/* your new image*/
You just set the image's width and height to zero to hide the real image and then you increase the padding on the image until its the size of your alternative image. Finally you paint that alternative image onto the foreground image's background.
I only mention it as a matter of interest and of course penders solution is the one you should go with.