Usually, you won't manage just a few images but probably hundreds or thousands, so having as much information as possible about them is very important.
Using labels, we will be able to search for specific images by environment, as follows:
$ docker image ls --filter label=environment
REPOSITORY TAG IMAGE ID CREATED SIZE
myapp 1.0 7dad160a2b02 4 seconds ago 5.6MB
myapp latest 285c3d16e672 7 minutes ago 5.6MB
$ docker image ls --filter label=environment=test
REPOSITORY TAG IMAGE ID CREATED SIZE
myapp latest 285c3d16e672 7 minutes ago 5.6MB
$ docker image ls --filter label=environment=production
REPOSITORY TAG IMAGE ID CREATED SIZE
myapp 1.0 7dad160a2b02 18 seconds ago 5.6MB
$ docker image inspect myapp:1.0 --format "{{ index .Config.Labels }}"
map[environment:production]
Remember...