So, this is one of those things you might never see / never know about, but the embassy is actually pretty good about getting info out. The Musée Carnavalet is actually a pretty amazing place. It's an old residence converted to a museum, but the collection is quite vast. I took zero pictures, but they have so much too see.
This was cool...a room from the World Fair (1900s, I think) created by Alphonse Mucha. This picture does it little justice, but those peacocks are metal. They have colored glass in their tails.
This is a pretty amazing room when you realize it's from the early 1900s. Here are some more good pictures. You need to remember this was from the beginning of the 1900s and no one will talk of this person as a "famous" artist but he had some impressive ideas.
Another impressive work was an entire ballroom. You can see it here:
It's very dark but at the same time very moving. Easily my favorite room at Musée Carnavalet.
There are some other pictures here: http://nic-nakcastle.blogspot.com/2011/05/carnavalet.html
Here is the guide book. This is a great museum and highly recommended.