To use an image for a submit button type the code below into the code view of
your page. Change "yourbutton.gif" to whatever image you want.
<input type="image" name="submit" src="images/yourbutton.gif">
However it only works for the submit button not the reset button - although there
are other methods using javascript to make an image/button and javascript code to
reset the form - that's a little more complicated.
Also, you can use styles to change the way the button looks (add a background
image for example) or change the borders,fonts colours, patterns etc and turn a
boring grey button in to some fancy creation!
To use the styles, just right click the button, and go to form field properties
then choose "Style".