When you've got a class set of iPod touches, it's important to number them. Not only should the device's name (set in iTunes) include its number, but the number should be visible somewhere on the device. Some schools have numbers engraved by Apple. Others write with permanent marker or place a sticker on the back. Numbering classroom devices is important so that students and teachers can quickly identify the handhelds. Classrooms that are lucky enough to have a syncing/charging cart or tray typically number the slots so they can quickly see which iPods are missing.
Most schools are putting their iPods into protective cases, which is a great idea. (I like the 92¢ silicone cases from Monoprice.com.) The problem is that the case covers the engraved number or sticker. Stickers tend to fall off cases and marker rubs off.
An innovative way to identify iPods touches is to set the wallpaper image of each device to include its number. This way you can simply press the Home button and the screen instantly lights up and displays the device's number. Wallpaper can be any image that's in the Photos app. That includes images synced using iTunes or images saved from mobile Safari or other apps.
I've made three sets of images that you're welcome to use as wallpaper. You can go to a webpage for the collection of images below you'd like to download on each iPod touch and save the image of the number for each handheld. Or, better yet, have a class do this and it will take just a few minutes.
Alternatively, you can download a zip file that contains 50 images. You can unzip the file and sync all the images to all iPods. Then on each iPod set the image with the proper number to be the wallpaper image. Don't worry, if you delete the original image, it does not affect the wallpaper.
Of course you can certainly create your own images with desktop graphics software like Photoshop or GIMP. The resolution of an iPod touch's screen is 480 pixels by 320 pixels and it's helpful to make your images that size. In your images you might want to include your school or class name or logo along with the numbers. You might even want to color code numbers. Something else that could be fun is including the name and/or photo of the student to which the handheld is assigned.
Unfortunately, there's no way to lock down the wallpaper image on an Apple handheld. While students might switch the wallpaper image, let them know the importance of not changing the number.
Perhaps students would like to create their own wallpaper that includes their numbers. They could make their own images in a drawing app like iDoodleIt and save their images to Photos or take a screenshot. Then from the Photos app they can set the saved image as the wallpaper.