For larger snakes you would need to gut them before the process as you would hear the decomposed matter sloshing around inside.
*shiver* Yuk!
You can neutralise the toxicity of waste cyanide solutions with a molar excess of caustic soda (NaOH) and hypochlorite bleach (NaOCl or CaOCl) to form non-toxic cyanates.
Ideally you'd need to remove decomposable organic matter from the metal form and to achieve this I suggest this:
When you apply your conductive 'activator' coating to the surface leave a +/- 3mm strip down the length of the belly uncoated using a brush or if spraying using a strip of tape or soft wax.
Prime it in the cyanide copper bath, rinse thoroughly and then leave it in the acid copper for a good while to ensure a fairly thick layer of copper on the skin. Use brighteners in your acid copper bath to get a good lustrous finish, the better the surface finish the better your silver coat will look.
Now wash the animal throughly to ensure there is no trace of cyanide and leave it with flesh eating fauna such as maggots or mealworms for a few days/weeks. Once the skeleton is exposed you might want to soak it in water from time to time to soften the bones for the fauna to consume. Edit: you could also burn the organics out in a oven or a fire but a good clean afterwards is very necessary.
Eventually you'll be left with just the copper you plated on it which is at this stage very fragile. Now soak it and brush out any organic remnants inside the copper skin leaving a clean metal surface, very important that it is clean properly. Apply an inhibitor (wax) to the outside only and place it back into the acid copper bath to thicken the copper skin from the inside. The thickness should be such that it's rigidity is good enough to be handled without deforming.
Once you're satisfied, a 20 second dip in a silver tank will give you the end result, just don't forget to rinse it properly.
Just remember this sort if thing is governed by the sh!t in sh!t out rule, if you slip up somewhere in the process, the end product will magnify your boo boo tenfold.
Out of curiosity, what are you using to activate non-conductive surfaces to plate on?