If you have the ability to upload Wallpaper files to your iPhone or your iPod Touch then you need to know the proper size. The default wallpaper files are located in the /Library/Wallpaper directory and include the default wallpaper files and the thumbnails for those wallpapers. To get the iPhone wallpaper to display correctly you need the proper sizes.
Setting a personal image as the background for your iPod Touch is easy. Follow the instructions below.
First you have to sync personal images from iTunes to your Touch.