I don't think flowers are any more interesting than bikes either. Anything can be the subject of a great piece of art. The most beautiful thing in the world could be painted in a very boring way, and no one would ever care about the painting, despite its beauty. Likewise, the most boring and ugly things can be turned into the most beautiful and interesting works of art. It all depends on what you, the artist, make of it. You have to make people see things in new and interesting ways. If you just paint a bicycle, you haven't done this. Try the O'Keefe thing and paint a bike that looks like a vagina.