iOS5 Photo Stream keep your photos synced between devices and Mac/PC. If iCloud stores lots photos in your Photo Stream and you don’t need, you’d better reset Photo Stream to clear out all pictures.
How to reset Photo Stream in iCloud.com
* On your Mac/Windows, open www.iCloud.com and sign into using your Apple ID and password.
* In the upper-right hand corner, click on your name > click on ‘Advanced’ from the Account Settings.
* Click “Reset Photo Stream”. iCloud will notify that “All Photo Stream Photos will be immediately removed from iCloud”. Click “Reset” button to confirm that. If you get a “Server error” when trying to reset photostream, go to deal with Photo Stream from Safari Browser. Don’t use IE.