Please use the following codes in your Theme Options -> Custom CSS
background: #999999 none repeat scroll 0 0 !important;
border: 1px solid #999999 !important;
Result screenshot. http://prntscr.com/8eagiu
Sorry, I have never use that plugin you mention, in fact, I have never use any of the woocommerce premium plugins. Sorry, I have no idea if it will work with our theme.