New buttons - custom icon/size?

New buttons - custom icon/size?

I have been using the older development version of the jQuery buttons from the wiki which had a size option and allowed a custom image for an icon. After upgrading to 1.8rc1 the buttons don't have a size option and can only use the built-in icons.

I guess I can change the size myself with css but what would be the best way to have a custom icon?

Thanks