Experiment for yourself! Live a little!
Oh, all right .... maybe it is a bit on the advanced side - even Google would have trouble finding it (it keeps turning up the JavaScript-driven <a href="#"> thing you had).
input
{
background-image: url(http://www.phpbuilder.com/images/logo.gif);
border: none;
background-color:navy;
color:transparent;
height:55px;
width:130px;
}
<input type="submit" action="http://www.example.com/" />