When using a computer (or phone) it’s nice to give it that personal feel. I love me a good wallpaper. Some are inspirational, some are colourful, some are nice and clean. I used to lose hours on websites like these to embiggen my wallpaper library. Just sifting through wallpapers like others do through vinyl or photographs. Enjoy responsibly (and sorry for making you waste your time ;) ).
Computer wallpapers / Wallbase.cc
And why not look at some of the world prettiest pictures and make a wallpaper for yourself? Other photography sites that might provide some beautiful wallpapers by photos are: