How do I download a picture from my computer onto my ipod?
You can download a program call AVCWare iPod to iPod/Computer/iTunes Transfer to help you，
If you own more than one iPods, AVCWare iPod to iPod/Computer/iTunes Transfer can simultaneously manage all the iPods in the same interface, you may transfer files among these iPods by drag-and-drop.
Try these steps:
Connect your iPod to your computer. Select the iPod icon when it appears in the iTunes window (below devices). If the Photos pane does not show, click the Photos tab. Select your photo syncing options.