Sadly, it's an indirect search in most cases. By that I mean, you will easily saturate results if you go by generic keywords like longhair, hair, etc. But that's an essential step. Here's the playbook: you start with something generic like longhair. Open an image, see what else the user has posted, marked as favorite and if the image is in any group or album. You will then find so many keywords, groups etc that has great content. Branch out and repeat and rinse. For instance, while browsing recently I stumbled on an image of sorority girls. Boom, new keyword! Honestly, the list is endless.