iTunes doesn't really have much to do with the back up process as much as your device does...iTunes (and more often, iCloud) are just the storage outlets for the back up file (which is not something you can really go into and pull out specific "items" so to speak).
That said, if you want to get your backed up photos back onto your device, and you have not used iPhoto to sync these files before, you will simply need to restore your iPhone from the last backup that contains the photos you want, but this will, in turn, cause you to lose any new files/photos currently on your phone (so you will want to back those up separately NOT using iTunes/iCloud, so that you can sync the newer files afterwards).