A wise person once said, “There is no such thing as a free lunch”. That’s probably right but if you want to put up with Google’s tracking then you can use Google Photos for unlimited Cloud storage.
I actually use 3 services. I pay $24 a year for an unlimited Flickr Account and part of my Amazon Prime account provides me with unlimited photo storage. But, if you have google mail then you should be taking advantage of unlimited free photo storage. Every time I take a picture on my Nexus 5 smartphone the photo is automatically uploaded to Google photos for storage and editing.
How To Geek just posted a very informative article on unlimited photo storage