Saw these cute little frames and thought the idea would be fun to do in a guest bath. I've photoshopped my own little version. It's the last sign in this post.
Here's my design for a sign to put in a guest bath above the bathtub:
And I'd create a cute little "Sorry, temporarily out of order" sign to hang on it. I'd probably put a pretty little ribbon or nice black cord to hang it off the corner of the frame. A bit like this, but more ritzy..