You need to jailbreak your iPod.
If it is already jailbroken, then download BossPaper or WinterBoard (These are not the only two just suggestions)
Add a background image to the iPod Touch via the Photos tab while the iPod is connected to iTunes. You can then select the image in the iPod's settings and set as wallpaper. (See links below)
There was an update for the ipod touch about 7 months ago and it allowed you to change the background on your ipod and you can also change the lock screen
Only fourth generation only. Settings you go to app and click wallpaper?
it seems as tho only 3g ipod touch/ iphone 3gs only gets wallpapers. when you updated there should of been a default backgroud. other than that go to settings>wallpaper>set wallpaper and you will have the option to set home screen, lockscreen, or both
settings/wallpapers
you go to menu and stuff
http://www.pavtube.com/free_resources/how_to_put_the_wallpapers.html If you take a picture, then you can upload the picture as your wallpaper. http://www.poolga.com/.
is it from your pictures or drawings?
It depends on what ipod gen. you have. For ipod touch generation 1, 2, and 3, you can't put a background unless you jailbreak your device and get the right app from Cydia. For ipod touch generation 4, select the picture you want and set for your homescreen or wallpaper. As far as I know you don't need to jailbreak Itouch 4 to set a background. :P
Upgrade to iOS 4. It's free. It won't work if you have an old iPod Touch (before September 2009) or any 8GB iPod Touch. You'll need to jailbreak to get wallpaper.
To change the background on an iPod touch, navigate to pictures and click on the picture you would like as your background. There will be an arrow coming from the box, click on that and select make background. You can also download various themes which include backgrounds as well.
Set a wallpaper by going to settings>wallpaper Choose a pre-installed wallpaper or choose one from your photo library. On 4th gen, you can also set a separate wallpaper for the home screen. When you jailbreak your iPod touch, you can download winterboard themes to also change icons, battery icons, the dock, the lock screen, and much more.