They don't need a overly abrasive surface to properly shed...if anything, lots of rough edges might actually break up the skin as it comes off, resulting in more retained shed around the head and neck areas.

I set up mine with newsprint substrate, smooth round water bowls, and smooth plastic hides. I get one-piece sheds every time.

But as far as the original question, wood is porous, which can harbor mold and bacteria, which is not good in a warm, humid, enclosed environment such as your snake's cage.

Plastic is your friend.