Make sure you explain why you do not have phone logs or communication details.
Apart from chat logs, other things that you can provide are:
- Email transactions
- Photographs: not just those of wedding, engagement & honeymoon, but photographs showing all phases of your life together, including the dating/courtship period. You can (and probably should) also produce pictures which have you with your spouse family and vice-versa.
- Receipts of any gifts you purchased for your spouse and those he/she purchased for you
- Proof of joint bank accounts (statements or letter from a bank listing the account holders)
- Any joint financial decisions that you might have taken (like an investment plan/mutual fund/insurance you jointly invested)
- Boarding passes of any trips you took together or the trips you (or your spouse) made to visit each other
- If you are active on facebook, you may print the 'See friendship' page of you and your spouse. Hopefully, that shall provide some proof of relationship through 'first met', the common friends you have, pics of you together, etc.
- Receipts of shopping you did for the wedding
- Receipts/letter from the hotel or caterer for your wedding
- Greeting cards, letters or emails you received from your family and friends on your wedding/engagement. I have also known people printing a copy of facebook comments and submitting it to CIC.
Hope this helps...