Instead of numbering tables, a couple named each table after a destination they had traveled to.  Each table had a large sign in a table number holder giving its destination name and a photo album that served as a guest book, as well.  For example, one table was 'Rome.'  On the front cover of the 5" x 7" photo album was a picture of the couple standing in front of the Coliseum.  Inside the album were another four or five photos of them on vacation in Rome.  The back pages were blank for the guests at the Rome table to write their greetings to the couple.

If you want to be very creative, you can have a cut-out of a landmark from each destination, instead of the name.  The landmarks would have to be instantly recognizable, though, so your guests don't have to play a guessing game.  So for France, use the Eiffel Tower; for Italy, the Coliseum; for Greece, the Parthenon, for the United States, the Empire State Building...you get the picture.