In honor of Marathon Monday, here are a couple Retina wallpapers for iPad/iPhone. They don't take into account the Parallax Effect, but due to it being a solid color, doesn't matter if you have it on or off.
https://www.flickr.com/photos/srstarbird/sets/72157644168472251/
https://www.flickr.com/photos/srstarbird/sets/72157644168472251/