>>8378403They call it that because they want to. In truth, scale is pretty fucky. Like, both 3 3/4" and 4" figures call themselves 1/18 scale, even though they are dramatically different visually.
There are numerous ways to create hard plastic accessories. One is sculpting them out of whatever you want then making molds and casting them in resin. Another is building them out of plastic primitives like styrene sheets. And yes, 3D printers are also an option. My advice? Mix it up. Not everything needs to be plastic, and a mix of different materials can make for more compelling backgrounds. Look into woods and metal components that look good at small scale, etc.
