As others have said the right amount of holes and water would make the humidity work great. Newspaper is good since you can usually get a lot of it for free. The only problem that I see from newspaper is the ink will bleed off the paper and onto your snake. I don't believe there is any long term damage just temporary discoloration of snake usually to the belly.
What I'm looking to do is by a big 100' roll of white paper and cut it down to the size I need. I just need to find somewhere to order it at. I know Ralph Davis uses pre-cut white paper.