Create a vintage-style illustration featuring the iconic landmarks of London, specifically Big Ben and Tower Bridge. The artwork should be rich in earthy colors, evoking a sense of nostalgia and history. Big Ben should be depicted with its detailed clock face, while Tower Bridge showcases its majestic towers and suspension cables. The background must remain clean and transparent, ensuring the design is suitable for printing on a shopping bag. Integrate the word "London" in an elegant, stylized font at the bottom of the illustration, harmonizing with the overall vintage aesthetic. The soft, diffused lighting should enhance the warmth of the colors, creating a timeless feel that invites viewers to explore the charm of London.