I had a quick suggestion that may or may not be the best solution, but you could use liner paper to protect the walls and then using wallpaper paste to adhere the maps to the liner. I would talk to someone at a store like SW to ask them for suggestions. You could buy the liner paper there or online.

Sounds like a nice idea...I love the look of maps.

I saw something on TV - oh gosh, perhaps, I read about it... I don't know - anyway, instead of applying the maps directly onto the walls, they adhered the maps to large boards first (getting the designs "just right"), then mounted the boards-with-maps onto the walls. I'm sorry, it was a LONG time ago and I don't remember what the boards were made of.

I did this many years ago in my old home in a bedroom. I used a wall liner and then pasted on old National Geographic maps that my Dad had saved for years out of the magazines. It turned out nice...however was a PIA to remove when I was prepping the house for resale...LOL.

Prime the walls with wallpaper sizing. Read the direction and follow carefully. Then use wallpaper paste to put the maps up.
Everything you need should be available at a good quality paint store.

Before you use those "old maps" for the wall, make sure they are not worth something.

I've always wanted to hang the funny papers in a half bath. Give people something to do while they........:)

I can't help with the technique but I can tell you a friend papered her guest bath with the old pull down school maps. The bright colored shiny-ish ones. I believe hers are from the 1940's and 1960's, Europe. I am so in love with that bathroom. She also used a vintage avocado green toilet. Who knew I would ever be envious of someone with an avocado green toilet. :D Good luck with yours.