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.