How can I back up my photos

you can't view the photos that you have backup either with itunes or iclouid.

you should be importing your pics to yoru computer http://support.apple.com/kb/HT4083

Photos are meant to be imported to your computer, like you would from any digital camera. Where ever you store your photos from your digital camera on your computer is where you'd store those from the iPhone

As the manual explains, you should be importing all pics taken with/saved by iphone to your computer regularly as you would with any digital camera.

iOS: Importing personal photos and videos from iOS devices to your computer

How to import photos http://support.apple.com/kb/HT4083. How to sync data to the iPhone http://support.apple.com/kb/HT1296