I can answer this a couple of ways. One is to say, yes, you may have a criminal claim against this man, depending on the nature of the photos sent.
The other way is to say, that your daughter is 17, the age at which it is legal to engage in sexual conduct in Florida, with or without her parents permission. The man is 20, not far removed from your daughter's age. I, as a defense attorney hate to see these things made into crimes, though sometimes they should be. If the man gets convicted, he will be designated a sex offender for life, with all the attendant consequences. Is he really a sex offender, or just your daughter's boyfriend and the both of them are doing what they want to, even against your wishes? Your daughter, it appears, has some complicity here. My suggestion is you forbid her to see this guy again and get some counseling. Don't let her have a cell phone. Locking this guy up may have a more negative effect on you and your daughter's relationship than trying to reason it out.
Mr. Waggoner's answer is a good one. I would suggest you talk to your daughter about this and get all the facts prior to making a decision as to what to do. The key to whether or not there is criminal activity would probably revolve around the nature of the requests for photos and the nature of the photos sent.
There are other charges which might be appropriate here, including contributing to the delinquency of a minor. If you are in doubt as to what to do, I would suggest you call a lawyer to discuss the matter. If you truly feel like what is happening is illegal, call the police. Make sure you have the telephone with the photos to show to the police.
Your primary responsibility is to protect your daughter, and if you feel that what is happening is truly inappropriate, bordering on illegal, then call the police and discuss it with them. You can always ask that they confer with the State Attorney's Office for guidance prior to them seeking a warrant or arresting the daughter's boyfriend.
The above is not intended as legal advice. The response does not constitute the creation of an attorney client relationship as this forum does not provide for a confidential communication.
There are a few ways this man may be breaking the law. Legally, as your daughter is over 16 and he is under 24, the act of intercourse between the two is likely not a violation of the law. However, facilitating your daughter's sneaking out of the house could possibly result in a charge of Interfering with the Custody Status of a Minor (a rarely used third degree felony). This would be a pretty weak case.
However, the man in question is in possession of child pornography. While he can likely legally have sex with your seventeen year old daughter, he cannot legally possess a naked or otherwise sexually prurient photograph of her.