I like all of them! The red snake against the black background is REALLY contrasting and looks fabulous. I agree that if you added green leaves (the complementary color of red) it would make it even more stunning.

The only criticism I have, is that the photos look a little too contrived on such a plain background. If you put some out-of-focus, dark, shadowy plants in the background, it could be even better. Then again, I'm speaking as an artist and not a photographer.