On the contrary, they are very photogenic if you set the shot up nicely.
and one more
Take advantage of their curves. One of the basic compositional tricks is to include an "S" curve in the shot. Snakes are full of these so keep an eye out for them. The tongue is also a bonus if you can catch it while it is out- it adds interest and action to the shot. Make sure the eyes and as much of the head as possible are in focus, this is the same rule as in portrait shots. If you are doing a macro of the scales, you will want to show texture or color depending on what caught your eye. If it is texture, try to get the entire frame nice and sharp, if it is color, go ahead and over saturate a bit (it is okay to do this when there is no reference color like skin tones to cue that the image is over saturated.)
Hope that helps.