hmm - yes, but you'd need to do it very carefully.
If you look in any example with a login you'll see how to set the property of a button, for the whole procedure.
In your case you want to set the image property, not the textvalue property.
AND you'll also need to set it, for both buttons, a lot closer to where the button is created. ie inside the VALUE::field routine for each field.
Cheers
Bruce