Add cosmetic items

[garsipal]

A while back, I tried out some cool cosmetic item models that matched the game's aesthetic quite well, and the best part was they came with free licenses. With these available models up for grabs, it's relatively a piece of cake to finally fulfill the original vision of allowing players to customize their look a bit more.

Cosmetic items would only be available for two body parts:

• head/face (hats, helmets, masks);
• back (backpacks, swords, guitars);