Sence the ex employee no longer works for the company, does he have credibility
Credibility doesn't sound like the issue. There is a pretty clear line of from the employee, to the ex employee, to you.
Whether there is a case depends on a lot of facts we don't know, like: what do the photos show; why did you send them to the ex employee; did you know or expect that the photos would be circulated to others, especially those still in your employ; what is the relationship of the ex employee to the employee; what kind of "case" are you asking about; and, many other questions that might arise if we knew what you were talking about.
Your question is unclear. If you are asking if you have a case, the answer is likely no. If you are asking if the offended employee has a case against the ex-employee or you, more would need to be known but possibly. Of course, the nature of the pictures would be important to understand. A meritorious claim of sexual harassment in the workplace requires unwelcomed comments or conduct of a sexual nature that are so severe or pervasive so as to fundamentally alter the workplace, rendering it hostile to the offended employee as a sexual being. Whether one text can be considered severe or pervasive will depend on the text and other circumstances.
Just because someone is no longer employed at a company does not necessarily mean they are not going to be considered truthful. Many factors would go into that judgment.
Good luck to you.
