Google+ Now Lets You Pick Individual Local Folders For Auto Backup was written by the awesome team at Android Police.
Apart from the Camera roll, most media folders on your phone don’t need to be automatically backed up to Google+ (if you use the feature). The images you downloaded from Twitter or Reddit, or the memes you received via WhatsApp or Viber are mostly disposable media files you view once or twice but wouldn’t miss if they were gone. There are, however, a few folders that you may want to back up, like the one with the images you’ve received via NFC or the folder your third-party camera app uses.