Where can I find the list of GCR public images? In case of docker images, we can list it in hub.docker.com. But I couldn't find anything like that for GCR.
tl;dr There is no such thing, at least today.
GCR is first and foremost a private registry. However, we respect the ACL's that users put on the GCS bucket backing their repository. This is how we offer anonymous read to buckets like:
Given a specific project, you can search within it using:
docker search gcr.io/google-containers/<substring>