iTunes syncing to iPods (that are not iPod touch) mostly goes one way, from computer to iPod. For photos, at the time you synced the photos to the iPod, there is a setting that you needed to have enabled in iTunes if you later want to recover them from the iPod. This setting is on the iPod's Photos tab in iTunes (where you set up photo syncing). There is a checkbox for Include full-resolution photos.
IF that checkbox was checked, you can Enable disk use on the iPod's Summary tab, and find the full-res photo files in the Photos folder on the iPod. Otherwise (if setting not checked), when iTunes syncs the photos to the iPod, iTunes converts the images to a very low-resolution version that is optimized to fit the small iPod screen and stores the image data in a single database file (to save storage space). There may be third-party software that can extract separate photos from that database file, but the resulting photos will look bad blown up to computer screen size.