One of my favorite restaurants in New York, Cafe Cluny has papered their two restrooms in botanical and bird prints similar to Steven's powder room. They are small spaces but I love the thought they put into making them pretty. One interesting thing they have done since it's a public space is to cover the walls with clear Plexiglas to keep them clean and dry.
LA based interior designer Schuyler Samperton has papered her powder room with post cards and pictures. I wonder if it started out with a few and then expanded outward as time went on.
I also love that Schuyler Samperton propped up photos on a shelf in the same bathroom.
Artwork can become like wallpaper if it's hung en masse. The limited edition Love posters by Yves Saint Laurent that Polly Mellen has framed and hung in her bathroom add color to the otherwise all white room.
Just in case you want your guests to remember who you are or where they are, you can paper your powder room with own photo or book cover like Candace Bushnell.
Marion McEvoy has also hung framed photos of herself in her powder room. There's something cheeky about this that says that you don't take yourself too seriously.
One of my all time favorite powder rooms is at the J. Crew Collection store on Madison Avenue. The striped walls are fabulous but what I love are the Hugo Guinness prints that line the walls.
Interior designer Amanda Nisbet also lined the walls of a powder room in the Traditional Home Designer Show House in Hugo Guinness prints. The funniest part is that she swapped out the mirror for a chalk board. I wonder how your guests would react if they couldn't fix their hair or reapply their lipstick! I bet that would definitely elicit a big wow!