Your neice could sue for specific performance of the contract or for money damages. First, I would send a demand letter first demanding the photographer provide the pictures pursuant to the contract.

If the contract is in writing, you have the option of filing against him in a small claims court which would be less expensive than suing. The written contract is important in that it proves the components and where there is a breach in the agreement. I would suggest that attempts to reach him be in writing establishing your paper trail. If you call, document the time the call was made. There is not a way to force compliance when one doesn't want to comply other than going to court.

Judge Joe Brown and Judge Judy have successfully tried cases involving wedding photographers who didn't uphold their contract. I suggest you contact their shows and get your money back. That is a milestone event in your life that wasn't documented properly.