Subtly mirroring the design of its new sister site Flickr, social blogging platform Tumblr revealed a new-look homepage for a handful of lucky users on Thursday. With what used to be a fairly basic log-in page (below), the new photo-rich design displays a different photo each time you visit the site, showing a range of images from landscapes and animals to art and illustrations. The upgrade occurred only weeks after Yahoo announced its $1.1 billion Tumblr purchase, with the move expected to encourage more users in the 18 to 24 year old age demographic and improve its social strategy.