Now that you have decided to spice up your hangers, you are going to need some things.
Why Wire Hangers?
Wire hangers are nice and thin and have a consistant thickness throughout the whole hanger.
Plastic hangers tend to have variations in size, particularly on the two ends, and usually have some different plastic pieces hanging out (those hooks used to hold up those extra loops on dresses).
Wood hangers already look nice on their own and are usually not in a circular path - meaning they are usually a wood bar so it would be harder to keep the yarn on without glue.