Hi!
Initially, we had collection of photos, and with this request, we realized then that just the photos was not enough. So, in response to the request, we added ticket receipts and photos of passport stamps, photos of cards and letters, and also sent evidence of insurance coverage as a spouse and proof of beneficiary for life insurance and savings account.
edit: also, for the initial submission, we had an affidavit from a family member, but maybe it is considered as a weak evidence.