These button where created using pure CSS, no-images involved. The icons are from a great fontFace kit. The way this works is simply added the appropriate style you would like, thus making the button appear a certain way. For example:
Download
This button contains the following class markup:
class="button sticker green icon dl"
button = Main button style.
sticker = Button Type: 'sticker, bevel, round, rect, round bevel, sBevel'
green = The color: 'green, blue, orange, red, teal, yellow…'
icon = If this class is present, then icon styling will be applied (not necessary on round icons.)
dl = actual icon to be used: dl=download, fb=facebook, twit=twitter, etc…