You can use white poster board. New white pillow cases. Pretty much anything thats very white. There are also differences in the pictures between using a glossy background as opposed to a flat or brushed background.
With black it seems better to use gloss or a mirror. With white i dont think it matters as much. Sometimes i have to play with the settings on my camera to get the color as close to real life as possible.
My only real problem now is i need at least one more light coming from the other direction to get rid of the shadow cast by the snake.
When I use the light, I normally have it on top of something (like a clear tub lid, or a screen lid that I use for an enclosure) so the light shines down onto the snake instead of having the light next to me in front of the snake. Here's an example: