Now, some of you may find this very similar to a certain post that I made a few weeks back, I consider this one different since it's much less exploitable and is also quite minor.
Each armour type would have it's own hat that goes in the helmet slot (except Leather and Chainmail, Chainmail would have none and Leather would have 2)
Leather would have 2, which would both by dyeable:
Cap, a simple baseball cap. Crafted by putting 1 leather on the right of a normal leather hat (The already existing Leather Cap would be renamed to Leather Hat)
Top Hat, a stylish gray top hat with a red ribbon around the brim. The ribbon would be the dyeable part, and it would be crafted with the leggings recipe, but with wool at the bottom line and a diamond in the middle, as this is only meant for the richest and most fine folks in all the land.
Crown, a tall, cartoonish crown with a huge diamond in the center. It would be crafted by surrounding a diamond with gold ingots, minus the top middle.
Medieval Helmet, a cartoonish "T-shaped" helmet. Crafted by putting an iron ingot on the sides of an Iron Helmet.
Diamond Crown, the Crown from before but Diamond instead of Gold and a big Emerald in the middle. Crafted by putting a Crown in the middle, with an emerald on top, surrounded by Diamonds.