An iPod can be synced with only one iTunes account at a time. once you switched to a new iTunes account or a new computer. You have to authorize your iPod to it at first, then you can upload music and video from the new iTunes to your iPod. But this way will overwrite the original files on iPod with the new iTunes. You may try this iPod transfer, it can help you copy files from iPod to computer for backup, you can also use it as an iTunes alternative to upload music and video. It will not erase your original iPod files. It's safe and works pretty well for me. http://goo.gl/fEA2j
In order to transfer pictures from the iPod to your computer, connect the cable into the FireWire or a USB 2.0 port on your computer and the other end to the iPod. To transfer the pictures to your computer after the connection, open the iTunes by holding the Shift and Ctrl keys, wait until the iPod comes up in the Source list under devices and might take a while. Locate the songs on your iPod and copy them to the folder on the computer. Have the iTunes make the transfer of the pictures to your picture library. For more details, check out http://www.ipodpctransfer.com/ipod-computer-photo.html and http://www.ipodpctransfer.com/pictures-ipod-computer.html.