The list of who can nominate is somewhat restricted -- but given that any member of any parliament, or any social-science professor at any university, can nominate someone, that doesn't strike me as a very high barrier to entry.
The bigger question, in my mind, is whether Snowden contributed to world peace. Yes, he clearly unveiled all sorts of schemes that the NSA had. It's a good thing for democracy that he did such things; it's clear that the US government was doing things that it claimed not to be doing, and that US and foreign citizens alike were rather upset to hear.
So yes, I'm personally glad to hear that these things were unveiled.
However, did this really contribute to world peace? Is the world a less violent place as a result? You could make the argument that it actually is more dangerous in the world, because the US is less able to spy on people. I'm not sure if that's the case, but it's not a totally crazy argument.