I don't want the wedding photos for a few days. I thought a deposit would be enough. The store demanded 60% of the liquidated damages. Is this reasonable?

That makes sense. The deposit is only a guarantee to fulfill the contract. If you don't shoot, you will break the contract and you won't get the deposit back. Now that you've finished filming, it means that the store has fulfilled their obligations, and only the work of taking pictures is left, and you have paid for it yourself. If you don't perform at this time, you must compensate the other party for the loss. Therefore, the requirements for the store are not too much.