Pinterest has been growing, rapidly, as the graph shows. If you're not familiar already, it's a site where users can create "pinboards" - groups of images that may or may not have a common theme. Tumblr is a bit more versatile, but the idea is similar.
eMarketer's Kimberly Maul says "“The platform works especially well for media companies, which can post their own content as well as supplemental photos and quotes. This has attracted brands such as The Atlantic, Rolling Stone and The Huffington Post. And fashion brands, including Oscar de la Renta and J.Crew, are leveraging the easy photo-sharing opportunities to include images of products, shots from fashion shows and more.”"