No, that is not how it works. Messages and Photos are sync'd via iCloud, which means that you need iCloud signed onto both your iDevices and your Mac.
On your Mac, go to System Preferences>iCloud and sign into iCloud with the same iCloud ID you have on your device. Once signed on, you will see the options that you can turn on to sync Messages and Photos.
Open the Messages app to see Messages.
Open iPhoto or Photos to see Photo Stream photos.
If you have Photos in your Camera Roll that are not in your Photo Stream, then you need to import those to iPhoto or to Photos on the Mac (unless you are using iCloud Photo Library).
You can see all of the data that is accessible in iCloud if you go to icloud.com on your computer and sign in with the iCloud ID that you are using on your iOS device and your Mac.
The backup that you do to iCloud from your iOS device is only that - a backup that is used to restore a device that has been wiped to the state it was at the time the backup was made. It it not related to the items you sync via iCloud.
Cheers,
GB