A Set Of Awesome Wallpapers: Desktopography
Desktopography is a website which shares a collection of impressive wallpapers to beautify desktops.
They are created by designers invited by the website and it can be clearly seen that "a serious effort is spent on each of them".
Wallpapers are published since 2005 and items are categorized as years.
They are provided in multiple sizes and besides using them, Desktopography is a good source of design inspiration.
Personally, I'm not a wallpaper fan and my desktop has only a black background, but now, considering to give wallpapers another chance : ).