Those of you who installed the first iPhone OS 4.0 beta released just yesterday, might have changed the home screen wallpaper.
One can do so via Settings > Wallpaper.
Unfortunately, the nice silver metal rain drops sprinkled default wallpaper that comes with iPhone OS 4.0 beta is not yet available as a photo in the 4.0′s library.
As a result, you cannot revert back to it if you changed the wallpaper just once.
At first, I did not find the original version in the wild but stumbled upon a really beautiful replacement. Download it from deviantART.
The original Apple wallpaper is available, too. Grab it.
Note: Do not sync wallpapers via iTunes!
iTunes tends to “optimize” images before sync, which makes them appear distorted when used as a wallpaper.
Instead email the image to yourself, open the email on your device, long press the image and save it to your camera roll.
Set it as your new home screen wallpaper and you’re done.

I am unable to set home screen wallpaper with my iPod Touch 2G. It is on iPhone OS 4.0 Beta. Please Help, thanks.
How to reset the iPhone OS 4.0 (beta) home screen wallpaper http://bit.ly/cHz6Md
This comment was originally posted on Twitter
Finally, the iPhone OS 4.0 Beta wallpaper is here. http://www.24100.net/2010/04/how-to-reset-the-iphone-os-4-0-beta-home-screen-wallpaper/
This comment was originally posted on Twitter
How to reset the iPhone OS 4.0 (beta) home screen wallpaper: http://j.mp/9qfCAn
This comment was originally posted on Twitter