Quad screen space wallpaper suitable for any Linux desktop: http://www.wallpaperpimper.com/wallpaper/Quad_Screen/Blue-Star-Field-5120×1024.jpg.
A nice 3D rendered wallpaper that features a lovely snowy mountains scene: http://i10.photobucket.com/albums/a121/Paul_D/ScreenShot00014.jpg.
This wallpaper is a super high resolution image suitable for about 6 screens, 7300*1000 pixels resolution: http://www.west-crete.com/img/panoramas/hania-harbour-panorama7large.jpg.
Get a good selection of dual monitor gaming wallpapers on this website: http://www.gamewallpapers.com/dual-screen.php.
Lovely San Francisco panorama for a quad screen desktop: http://fc01.deviantart.net/fs51/f/2009/264/2/7/If_you_are_going_to_SF_by_P_i_a_n_o_M_a_n.jpg.
Very beautiful Samurai wallpaper image. Lovely monochrome colors: http://images4.alphacoders.com/174/174564.jpg.
Nice swamp wallpaper with lovely afternoon lighting: http://m9.i.pbase.com/o6/08/681208/1/94606429.ghGtKWeD.3840×12005.jpg.
A nice city wallpaper with beautiful lighting and a perfectly placed sunset: http://www.wallpaperpimper.com/wallpaper/Quad_Screen/Wuppertal-5120×1024.jpg.