The popularity of mustaches this year is actually pretty amazing. You see them every where: Watches, necklaces, notebooks, stickers, clothes, etc. My little cousin actually has a fleece hat with a moustache on it, and it's adorable (it's from the Children's Place).
I think they're such a cute (somewhat silly) decor on basically anything.
Design: Cahoonas, http://cahoonas.deviantart.com/