Styling of buttons with images

Hei,

Does anybody know how to add image for buttons background? I tried to check in "TableTools.css".
I am thinking to use two classes: .excel og .print which predefine position for background sprite-image.

.icon-social {
background-image: url('../images/shared/icons-social-sprite.png');
}

.excel{
background-position: 0 -437px;
}
.pdf{
background-position: 0 -460px;
}

How can I apply/add these classes to excel and pdf buttons (TableTools panel)?

Are there possibilities to use Buttons options(http://datatables.net/extras/tabletools/button_options) for fixing this problem?

Thanks