What pictures are you referring to? Are they images from an app that are showing up in your Gallery? Or are you talking about photos that you're taking that are automatically being backed up to Google+?
If they're images from an app, it's probably because the folder that contains the images doesn't have a ".nomedia" file in there (which tells the system's media scanner to ignore that folder when searching for images to put in the Gallery). If you know the folder, you can create a blank file titled ".nomedia" using any file manager app. You might have to clear the Gallery's data and then allow the Gallery to repopulate (go to Settings>Apps>All, select Gallery, then Clear Data).
If you're talking about photos automatically saved to Google+, select Google Settings>Google+>Auto Backup, and turn it off.