No, I do not believe that Whistleblower Edward Snowden was merely trying to improve his own reputation by warning a group of European reporters that in the era of mass surveillance, journalists are increasingly a threatened class. It is so easy for the general public to get their own information now with social media that reporters aren't needed like they used to be.
Edward Snowden risked everything he had here in the United States to tell the world what he found out about the NSA's illegal surveillance techniques. He left his family, his job, his home to go on the run and make sure this information got out. I don't think he is concerned with his reputation. He just wants to make sure that the world knows these things are happening.
No, Snowden is not merely trying to improve his own reputation, he is making a clear and profound statement. Journalists are being threatened by governments that have too much power. If Russia does not like one of its journalists, it will do everything possible to remove that journalist from telling the story.
Snowden seems to have the best interersts of others in mind. His biggest motivation seems to be doing the right thing even if he loses everyone and everything he cares about. He nearly lost all contact with his family and his girlfriend, and did lose his job and his country.