Dog ears for the dog lovers, and maybe more over time :)
Some could be rewards from certain suggestions that add new dungeons and/or villages, maybe some from new NPCs we'll see eventually, as CA has mentioned it for "the next update" to be "most likely", but didn't come with 1.4!
More cute animal hats are always funny, and stuff like slime mask and hat (mask on the face, hat on top only.
I love more hats, and animal related ones can never go wrong, since it's about a farm, mostly!