How many pictures?

There realy is not a percentage that should be used, and not really a set amount. As a wedding photographer and the owner of my own company, I would expect no tip unless I went way out of my way for a family. Generally if the photographer is working for someone else (another photographer, studio, etc.), then I would tip $50 to $100, maybe as much as $200 if you receive really good service. I would not tip if the photographer is working for himself. If he/she brings an assistant, then tip the assistant.

Some people go as far as waiting for the proofs before tipping. This is completely up to you as the client.