There was similar debate when Apple's "Think Different" ads first appeared, with photos of Jim Henson, Martha Graham, Bob Dylan, Albert Einstein, Amelia Earhart, and more. Was it tribute? Crass commercialization? Is it any less OK because Mrs. Parks just passed away? Or is it particularly appropriate to mark her passing in a timely manner?
I think the tribute linked from the picture is a nice one, even if, as rjb5 points out, it seems surprisingly informal at first glance.