This is how you replace an form button with an image
<input type="image" src="picture.gif" name="optional">
Using the label element allows the user to click on the text associated with the form control instead of having to click the radio button, check box, select box, etc.
<label for="radio1">This Radio Button 1 has a label associated with it.</label><input type="radio" value="Selected" name="Radio" id="radio1">
<label for="first_name">First Name</label>
<input id="first_name" maxlength="40" name="first_name" size="20" type="text" />
<label for="last_name">Last Name</label>
<input id="last_name" maxlength="80" name="last_name" size="20" type="text" />