I traveled to England this summer. Great trip, but, of course, I was also fascinated with how the English advertise in the historic areas. Advertising and billboard-like signs are strictly limited. However, leave it to the British to find some extremely creative and highly tasteful ways to advertise.
I saw several of these bike boards in many cities. This particular one was in Bath. The advertising is bright pink, but so are the beautiful flowers. The bike itself seemed to add to the vibrancy of the city, not diminish it in any way.
It is like any advertising these days: Provide some real value (in this case some flowers) with your message and you can better sell your products and services. And, you can get around city ordinances on advertising.