Change standard button with personalized one.

Hello,first of all thanks for this great E-commerce software!

I'm triyng to change layout and make my own templates...It's very simply and intuitive,but now have a problem... I want to change the default buttons(Add to cart,Reviews,Search,Update etc etc)with my own personalized buttons made with photoshop.

How can I do this?
Thanks 

Thanks enigma1,now I can customize more my template!!!