That is covered here:
What kind of photos are you talking about?
Ones in the iPod's Camera Roll album are included in the iPod backup that iTunes makes. Photos synced to the iPod or not and they are not in your iTunes library either. You have to back those up separately.
Also the iPod backup that iTunes makes is not included in your iTunes library. It location is listed here:
iTunes: About iOS backups. So back that up too.