Here's how to configure Google + to prevent your publicly shared photos to be used as background images on Google products & services:
- Connect to your Google + account.
- Click on the Home button > Settings.
- Scroll Photos and Videos.
- Tick the Don't feature my publicly-shared Google+ photos as background images on Google products & services checkbox.
This document, titled « Google Plus - Prevent your photos from being featured as background images on Google products or services », is available under the Creative Commons
license. Any copy, reuse, or modification of the content should be sufficiently credited to CCM