“DATA STREAMING,” featuring late Luxembourgish artist Michel Majerus, opens at Kunstverein in Hamburg. Lost to a 2002 plane crash, Majerus made waves in the dotcom era for playfully integrating digital images—videogames, animation, desktop publishing—into his paintings. Now, a major retrospective sees Kunstverein and 12 German museums mounting exhibitions reviewing the artist’s work “with the hindsight of artistic and technological developments of the past twenty years.”