There is no back up service to iCloud. It's just not a feature of the service.
Most Simple Back Up:
Drag the iPhoto Library from your Pictures Folder to another Disk. This will make a copy on that disk.
Slightly more complex: Use an app that will do incremental back ups. This is a very good way to work. The first time you run the back up the app will make a complete copy of the Library. Thereafter it will update the back up with the changes you have made. That makes subsequent back ups much faster. Many of these apps also have scheduling capabilities: So set it up and it will do the back up automatically.
iCloud is not for backing up files from your Mac. The following is from this Apple document: iCloud: iCloud storage and backup overview:
What iCloud backs up
You have important information on your iPhone, iPad, and iPod touch. iCloud automatically backs up your device over Wi-Fi every day while it’s turned on, locked, and connected to a power source. With your device information backed up in iCloud, you can easily set up a new device or restore information on one you already have.
Here’s what iCloud backs up:
- Purchased history for music, movies, TV shows, apps, and booksYour iCloud backup includes information about the content you have purchased, but not the purchased content itself. When you restore from an iCloud backup, your purchased content is automatically downloaded from the iTunes Store, App Store, or iBooks Store. Automatic downloading is based on iTunes in the Cloud availability by country, and previous purchases may be unavailable if they have been refunded or are no longer available in the store.
- Photos and videos in your Camera Roll
- Device settings
- App data
- Home screen and app organization
- iMessage, text (SMS), and MMS messages
- Visual Voicemail
Your iOS device backup only includes data and settings stored on your device. It doesn't include data already stored in iCloud, for example contacts, calendars, bookmarks, mail messages, notes, shared photo streams, My Photo Stream, and documents you save in iCloud using iOS apps and Mac apps.
You should use local solutions for backing up files from a Mac. The easiest to implement is an external HD and Time Machine.