Right, you had a question. You may consider this as bad news, but -- assuming you have entered into an enforceable contract with the customer -- it would be improper for you to ask the retailer to remove the photos. You could only do that if the use was unauthorized. In this case, the use apparently was authorized -- you just haven't been paid for it. If the contract was fraudulently induced and the contract was rescinded (as explained in this case), you could proceed as an infringement action. But it's usually much more difficult to prove fraudulent inducement (the other party never intended to pay you) than to prove contract breach (the other party delayed paying you). Typically, in situations such as yours (and in this case and this case), your remedy is to sue the customer for breach of contract. That may sound wrong to you. After all, if you haven't been paid how can they use your images? So what's a photographer to do?
Some options. The gang over at PhotoAttorney state that it's possible to insert language into a contract that would permit an infringement lawsuit if payment is not received. The language indicates that no rights can be exercised until payment is received and that any such uses will be considered willful infringements. (The crew at ASMP supports a similar position.) We think the provision could be improved by adding a statement to the effect that, "In the event that rights are granted prior to payment to photographer, this contract shall be automatically rescinded." We can't guarantee the enforceability of the provision (because a court is the ultimate authority on whether a contract is rescinded), but it should come closer to meeting the standards explained in the cases cited above. BTW, you may want to check out our answer to a similar photo question.