I am not a lawyer, but it doesn't sound like any crime was committed, so the police aren't going to be able to help you. You can talk to a lawyer in your jurisdiction to be sure if any laws apply in this case, but if you publicly posted pictures, then they didn't steal anything by using them unless you had copyright notices posted with the images.
If a crime actually was committed, a lawyer would be able to help you to get it pursued. The police would then have to subpoena Facebook for the IP addresses of the account and then the ISP that those IP addresses belong to can be subpoena'd to get the user's information, but those both will require an actual crime to have been committed.
Such fake accounts are against the Terms of Service for Facebook however, so contacting them about it should get the accounts taken down. That is just because of Facebook's policies though, not some legal reason.