Flickr gives you 1TB of photo storage free but their app has been lacking the seamless integration with the OS and apps that Apple is promising.
Its a jarring experience really. you can look at 3 photos in a slide show, then in place of the 4th photo an ad. You can't even pay them to stop showing ads with your photos, as subscribing (which I did) only stops you from seeing the ads.
To keep everything backed up, I have a NAS in my basement that pulls a copy of my Flickr library on a routine basis.
Edit: Flickr Ad-Free is $49/year, but $24/year for grandfathered Flickr Pro subscribers. Sorry for the confusion.