Sounds to me like a standard copyright violation. Assuming you have proof that they're your pictures, then you should contact a lawyer. Since copyright violations aren't necessarily a criminal act, the police can't help you.
Instead, contact a lawyer and explain the situation: basically a competitor is using your copyrighted material against you. Then the lawyer will have to file an injunction against the company. In theory, the offenders will just be forced to remove the offending artwork - but there's a possibility that it'll go to court. I doubt you'd see any money from suing them, but they'll probably not want to bother with it and just remove the photos.
Sadly, lawyers aren't cheap.
