Not having a label, I just use Tumblr as a kind of picture blog for my own photos and the odd link to articles and videos I like. It seems pretty well disposed to visuals.
To me, Tumblr is just a modern extension of the kind of websites like Angelfire etc. that were around the late nineties, early zeroes. Just a bit more gracious to the eyes and a lot easier to use. But there's all sorts of online resources and I never really understand why one format becomes more popular than another, other than obvious ease of use.
Facebook's virtue is its immediacy - a label can make an announcement that'll reach a lot of people. It seems to have replaced email for a lot of people these days. I don't use it anymore, though - got sick of peoples' cats or what they had for dinner, among other things. Mind, if people started posting photos of their cats as dinner I might have stayed interested.