submitbutton/imagebutton

Hi, I'm kind of new to php so there may be an obvious answer but I can't find it for the moment. What I want to do is change the 'type=submit' of a submit button to 'type=image' so I can control the looks of the button. In pure HTML there is of course no problem, the image is still used as a submit button but... the submit type is being passed on to a php script ( ...if ($submit) {...) that makes a qeary to a mysql database. When I change the type=submit to type=image the script doesn't pick up the submit value anymore, so nothing happens. Am I overlooking something or is it just something that doesn't work? jan