I think the artist knows well enough about good design, painting etc. All his choices are intentional and probably have a meaning on some level. I know the different plants in the image represent different geographical aspects of Obama (one of them has to do with Kenya, another with Hawaii and the other mean something else).
@Julianna: The above video shows why if you really want to be a good painter, I think you have to get your mileage in drawing from life. In fact a lot of people should focus exclusively on drawing, and when I say drawing I don't imply just linear drawing. Lots of charcoal drawing, and ink wash drawings. It really helps you understand value and how light interacts. Otherwise all you will really be skilled at is copying photos, which there is nothing wrong with but if you want to transcend that I think you have to put a lot of hours into life drawing.