I've mentioned Docker Hub, Docker Enterprise Edition DTR (Docker Trusted Registry), and Docker Registry as three options for storing your images, but there are many 3rd party options out there.

Quay.io is a popular choice, and is very comparable to Docker Hub as a cloud-based image registry.  Sysdig did a Docker Usage Report in April 2017 based off their users that shows Quay as the most popular cloud-based choice.

If you're on AWS, Azure, or Google Cloud, they all have their own registry options that are well integrated with their toolset.

If you want a self-hosted option, there's Docker EE, Quay Enterprise, and also GitLab, which comes with GitLab Container Registry, among others.

There's a much larger list of registries over at the Awesome Docker list.