We sent similar stuff to Huron's suggestions. Immigration documents, leases, marriage certificate, travel tickets showing joint travel, photos of us on joint travel, and many other photos showing us over time in various situations, just the two of us and with our families and friends, etc. We also printed Facebook pages from the wedding time which showed congratulatory messages from friends. We sent copies of envelopes and letters addressed to both of us at our shared addresses for the wedding and otherwise. We each wrote a relationship history. We included some receipts (but not tons) from various significant purchases (wedding gown, wedding suit, etc) and important dates/outings (somehow I ran across our first date receipt while putting this all together!), and even a couple showing our normal routines (like getting thai take out). We included copies of cards and letters we wrote each other over time, some photos of Valentine's Day gifts (because I had them), and documentation showing our shared cell phone family plan. I also sent bank documentation showing he is my beneficiary.
Hope this helps!
