I once asked the question "Why do computer users cover their desktops with wallpaper?" on an Internet newsgroup, to which someone very wittily replied, "Because they spend so much time cutting and pasting."
Anyway, here are a selection of wallpapers at various resolutions.
Select the photo you want to download and your desktop resolution. Click 'Go' and the photo will then open in a new window.
When it has finished downloading, you can then right-click on it and choose "Set as Background"/"Set As Wallpaper" (depending on your Browser) or "Save Target As…"/"Save Link Target As…"/"Save Link As…" if you want to set it up manually.