Once again today, as I was browsing through some portfolios on the web, I saw several attempts at glamour and beauty style portraits where the subject was incongruously holding a flower, had a flower in her hair, or had a flower lying upon her or beside her.
I can only assume that the thinking of these photographers was something like: The girl is pretty. The flower is pretty. If I photograph them together, what a pretty picture I will make!
Of course, it doesn't work like that. With few exceptions, a strong graphic composition has a single centre of interest. If you're photographing a girl and a flower together, then what is your image about? There is almost no way that including a flower in the frame is going to accomplish anything more than detracting and distracting from the statement that you are trying to make about your subject's beauty and character.
Start by deciding what the centre of interest is in your composition. Often in a portrait, it is your subject's eyes. Then follow the basic principles of composition to frame and balance the rest of composition around your chosen centre of interest. Be ruthless about omitting needless elements. If something in your composition is competing with your centre of interest for attention, or even if it is just failing to do enough to strengthen the composition, then get it out of there.
(The same point can be made about post-production treatments. If all that your treatment is doing is subtly reinforcing your compositional choices, then go for it. More often, though, what I see are treatments that add unnecessary stuff which dilutes the centre of interest.)
Are there cases where adding flowers to a beauty or glamour portrait makes sense? Sure, if the flowers are fundamental to a design concept, and are integral to the basic composition. What comes to mind are the two images that were used in the promotional posters for the film American Beauty: the rose held to the belly, and the character immersed in a sea of rose petals. Those images still managed to cleverly adhere to compositional rule #1: simpler is better.
I suspect that some of us use elaboration and ornamentation to try to hide a lack of confidence in our basic portraiture skills. One truth about photography is that there is always more to learn, for all of us. Invest in learning to be good at controlling light and shadow, lines and form, and effectively communicating with your subject. With practice, you will never need more than that, to reveal and photograph the beauty in your subject.