I think Depeche Mode's Broken Frame is beautiful, Duran Duran's Patrick Nagel art print cover on Rio defines the flashy side of NW for me while debbie harry's Koo Koo is quite disturbing but so artsy. Other ones that come to mind..
Kraftwerk - Trans euro express
XTC's album covers are nice and expressive to me
Kate Bush's covers are horrible to me, the operatic quality of her music is nice in sound but when translated visually, it's almost too cheesy and old fashion for me, but she was really the only one doing that so in that sense she did stand out.
