I'm not sure about a familiar, but as a pet sure. I know Sallaron had a pet White Faced Belarian Monkey named Screech for the longest time. It had no mechanical benefit but sure was fun to RP with. I believe a GM even gave him a certificate of ownership and an icon to carry in his inventory.
Still a snake is not really quite friendly, I don't know if even animal empathy can be used with them, On a wizard familiar it would be a bit more tricky due the bond beetwen the master and the familiar.
You can add new familiars. Someone at one point redid the system more to PnP style and put it on the vault, as well. It's just that you can't just add a snake and call it done, heh. You have to add all 40 levels of snake and someone to balance it and all that. I never really liked most of the familiars, especially when DMs were still trying to tell people it was a "low magic" world. It doesn't really matter as much anymore, even if some are still kind of silly, or would be more fun to only be accessed later.