In an attempt to see how I can best use keywords to help my images surface near the top, I've been carrying out random searches and looking at the keywords of images that appear first. The result is quite surprising. For example, a search for "tate modern" returns a picture in first place where the word "modern" appears only once, not as a keyword but in the caption. There are only eight tags in total - and they are all single words. So much for poor discoverability. I'm in no hurry to flesh out my keywords - in fact it's more likely that I will start a wholesale purge.