I have an idea but it involves using celebrity images. Is this illegal? Can I be sued?
If you intend to use celebrity images (or any else's image, for that matter) for a commercial purpose, you must obtain the permission of the individual, who will likely want you to pay for the privilege . . . and if it's a celebrity, pay handsomely (why do you think sports figures command multi-million dollar endorsement fees?). Using their image without permission will almost assuredly result in a lawsuit. Contact an attorney who is knowledgeable in this area and who can properly document the transaction.