The standard benefits as listed on the Star Alliance website:
Star Alliance Silver Benefits
* Priority Reservations Waitlisting - when there aren't any seats left on your preferred flight, gives you priority should a seat become available.
* Priority Airport Standby - gives you top priority when standing by for a flight at the airport.
Besides that, there is nothing else that bmi offers to *A Silver members with the exception of their own BD *S flyers who get lounge access and a free meal deal on-board.