Wonder Walls is my brand new favorite company that specializes in affordable custom-made wallpaper. Nestled amongst their creations are these London Wallpapers.
This collection features iconic images such as a London bus phone boxes and the Union Jack. From these basic images you can then choose your own print sizes and colors. I am quite taken with the punk rock one.
They also have a number of other awesome wallpaper designs such as the skulls and stars pictured.