I couldn't find anyone who had done a fox mask so I tried making my own because I'm a huge folklore nerd and I love foxes. 

Just a disclaimer, I'm no modder nor pixel artist. All I wanted was a fox mask and if anyone else wants one but is lazier than me, here it is.

I'm not sure how Content Patcher works so I'm just leaving the .xnb file here with only the fox mask added. Anyone can just edit the mask into another pack of hats or whatever (just like I'm doing, but I can't upload hats that aren't vanilla and weren't made by me).

If you don't know how modding with .xnb all you have to do is find the appropiate folder (in this case it's the Farmer folder, Disk C > Program Files > Steam > SteamApps > common > Stardew Valley > Content > Characters > Farmer) and you replace the vanilla one with the "modded" one. Never forget to back up your vanilla files or you'll hate yourself for the rest of your life.

That's it. It's just a stupid fox mask.