They selected names of "things" (cities, places, dates, etc.) that were meaningful to them as their table numbers. I love that idea and it's a great alternative to just numbering the tables. You could even take the naming a step further and do a double sided table card with the "name" on one side and a description of why that name is significant to you and your beloved. Giving your guests some great conversation material while they're waiting for the party to get started.
A few more tips ... keep table cards large enough to read but small enough not to compete with other table decor, decide whether you will need a stand/holder for your table cards or if you want them designed like a tent to stand on their own prior to ordering and have fun with them!