Having empty chairs across from the bride and groom is a Scandinavian tradition. The signs aren't necessary, guest just know that they are invited to come and chat. This is a simple way to take the pressure off of the bride and groom to do a receiving line or make it around to every table to greet everyone. This way the newlyweds can actually sit and enjoy the meal and it's up to the guests to say hello.
This is such a fun idea for the morning after the bachelorette night (and even the bachelor party too!) Could be used as a personal Bride/Groom keepsake OR also gifted to the bridal party after the Wedding has taken place. Could also have a picture like this for the morning of the wedding!