NicoWall is a wallpaper management application.
It change the wallpaper automatically with images of NicoNicoSeiga ( http://seiga.nicovideo.jp ).
It's not require account of NicoNicoDouga, you only have to choice your favorite 'Clip' .
('Clip' is a feature of NicoNicoSeiga like photo album)
Of course you have account, you can create your own Clip.