Mirrors aren't meant to be kept hidden in the bathroom or bedroom. Of course they serve a very important purpose — they help keep us looking our best but that doesn't mean they can't look their best as well. There's so much potential for mirrors and they can really help bring life to a room.
Mirrors in the entryway are always a huge hit because they add some serious drama when first arriving but they also serve as a last stop check point on the way out. If you have a small entryway, adding a mirror will make the space feel larger and won't have guests feeling cramped and cluttered upon entering.
In the living room, adding a large mirror above the fireplace will help offset the rustic elements. A mirror is also a great alternative to hanging the television above the fireplace! There's no wrong place to hang a mirror (well, maybe above the bed!) but keep mirror to furniture proportion in mind and you'll be fine!
Images: As linked above.