I'm not a huge fan of storing my photos online, unless it's on a server that I have direct control over, especially with respect to backups.
That said, Google Photos seems to be OK. It's an integral part of their Google+ service, and I believe that pictures taken with a Google Android phone (like the Pixel) are set by default to upload a copy of the photo to Google Photos.
If you want to store full-resolution images online, you may be better served by something like 500px or Flickr.