When I was at college, I lived near the tiny Tippety Wichity Island in the St. Mary's River. I had framed a chart of that section of the Chesapeake Bay in the guest room at my old house. So as I was flipping through Carleton Varney's Book of Decorating Ideas, I found that he thought maps were "in".
CV talks about having a seaman's map of the Virgin Islands with their course from St. John to Tortolla pencilled in. He says that maps give a personal look to any room. Use maps of places you've been and places you'd like to go. Surround a framed map with photographs or memorabilia from that special place.
When I was in college, I took a navigation course (I practically majored in sailing) and so have a great affinity for charts and maps of all sorts. Nautical and navigational charts are especially pretty in their pale blues, greens and yellows. An old office of mine was papered floor to ceiling in charts of the Chesapeake, and we would often have to stand up on the desk to find some point or creek.
I use maps a lot in my graphic work and recently took a map of Nottingham, where my father grew up and added a picture of him at school. I took an 1940's road atlas of the UK and scanned in the south Wales coast where I used to live. I superimposed a photo of "my" two Welsh kids in the bathtub and sent it to their father as a present. I made a birthday print for an old friend with a vintage map of Paris, a photo of the Eiffel Tower and a street sign, along with her initials and a pair of stiletto heels.
You can find vintage or antique maps on Ebay for less than $10 or framed reproductions in catalogues. Stores specializing in old prints and maps are also a great resource and you can find some quite obscure things if you look. You can even frame a 1960's gas station map showing the route of a favourite road trip.
I agree 100% with Carleton - maps ARE in!