I did all that stuff to begin with, to fit in with the iStock "controlled vocabulary"... "large group of people", "selective focus", "elementary age child" and so on. I very soon grew tired of it and for me at least, images without it don't seem to sell any worse than those that that have it. I still use "abstract", "backlit", "motion blur", "silhouette" and a couple of others that I'm guessing people might use as search terms, but that's about it.