Okay, I’m a terrible artist, so I can’t really draw/model anything, but I thought of a few interesting things. If one of the new biomes has some type of radioactive/luminescent mushrooms, it would be neat to see them as a low quality source of light (such as on the end of a stick, like a makeshift torch, for lighting up your house, etc.) Or, as a bow improvement have a circle of metal affixed to the bow with 3-5 bone splinters, and on the end of each splinter, a small piece of mushroom to help you see as a sort of sight. Kind of like this (I know it looks terrible, I know xD):
That, or possibly an enemy covered in mushrooms in caves during the day (comes above ground at night) that will glow brighter when it is attacking, or go dim when following you. When killed, maybe you could harvest the mushrooms from it, attach wiring to the nerves on the mushrooms, then power them using a power source (if ever added to the game, such as a wind/watermill/generator or something) to make them glow as a way of lighting up your house. Probably a terrible idea, but I figured maybe somebody would get a kick out of it, with the whole mutant idea really coming up.