Love the idea of having table numbers with meaning. For example "5: Day in May we met." That would be really difficult though, but I guess you wouldn't necessarily have to use consecutive numbers. Another cute - yet potentially embarrassing idea - is to have pictures of the bride and groom at ages corresponding to the table number. Finally, I like the idea of using locations instead of numbers (though I guess a number could still be included). The cards could have pictures of meaningful locations such as where the couple met, first date, etcetera and a short explanation of why it's meaningful.
Now the centerpieces. Where to begin? How about some "nontraditional" ones...
And here's some DIY centerpieces without flowers. If done right, pretty paper flowers or egg-carton-vintage-button ones can be a nice substitute. Or check out these vegetable oil filled mason jars that give the pictures inside a vintage appearance. You can even add dried flowers like lavender inside.
Finally, I have to post some floral centerpieces: