Promotion SPOTTED. Christie’s | Tumblr. Famed auction house Christie’s announces a special event with Tumblr where Lichtenstein’s late masterpiece, ”Seductive Girl” will be both featured at Tumblr’s headquarters and streamed live as a Q&A event. Certainly interesting to see bigger brands increasing their involvement with new platforms. Christie’s is obviously interested in reaching the coveted millennial demo. So, keep your eye on the Tumblr feed. Ready or not, here comes the marketing. I know how you must feel, Brad…