http://webdesign.about.com/cs/forms/a/aaformsubmit.htm
<input type="image">
Using an image makes it very easy to make your submit button fit with the style of your site. But some customers don't recognize it as a submit button .
http://webdesign.about.com/od/htmlta...s_inputimg.htm
<input type="image" /> Web Browser Support:
....
Internet Explorer 2, 3, 4, 5, 6

e poi
http://shatsar.blogspot.com/2009/07/...typeimage.html

non basterà... ma almenno ti ho aiutato a confonderti le idee


EDIT:

forse questa discussione su codingforums ti può interessare