Depending on who you choose as your officiant, you can totally customize the ceremony with any elements you want. (I've seen custom vows, sand ceremonies, rose ceremonies, wine box ceremony, etc.)
I've also seen people make/bring their own special bouquets/boutonnieres or decorations for those, such as charms, pins, etc.
The music you choose will personalize the event.
You could probably bring your own cake topper and cake knife/server.