you can set the new Nautilus background in two ways:
1) uncompress where you prefere the file and select it from Nautilus: click on the "edit" menu > "backgrounds and symbols" > "select file..."
2) as root, place the new background in the main patterns directory in /usr/share/nautilus/patterns, then, from Nautilus, select it from the menu edit > Background and symbols
thank to mr ~grevenlx for his masterpeace source file
remember to vote! please.