Pine shavings or pine chips can give off large quantities of volatile oils called terpenes. It is generally accepted these are not good for animals in cinfined spaces. Aged chips or shavings or pine bark will not produce anywhere near as much and is therefore acceptable as a substrate.
Large laterite pebbles or large aquarium gravel is great if you want a naturalistic look. Line the bottom of the enclsure with some 200um black plastic, rove the soiled gravel and wipe the plastic and disinfect it before replacing the gravel removed. Soiled gravel is readily cleaned and can then be be reused.
I would also rcommend the coir fibre, either coarse chopped (for mulch) or the fine chopped (potting mix additive). Cheap, safe and many snakes love burrowing under it.
Blue