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I think I found a really dope site housing multiple galleries of hair styles dealing with today's trends. Could be most useful for artists working with futuristic concept art. Just pick a brand and it'll lead you to their galleries. Unfortunately, they're not hi-res, but I believe they're viable incase you wanna download the images and keep them in your reference morgue.
Hope this helps, 'cause I'm definitely gonna use it.
Learn it. Live it. Love it.
Thanks for posting this!