For the `h:graphicImage` I think there is some caching going on with the browser or `nginx`, so they think there could be no changes. Not really sure about this theory.
In this case, the `cms` already returns the `img` tag with the URL reference, so you just need to show it with an `h:outputText` with `escape=false`.
Just change the `locale` of your session then update the `h:outputText` then the image should be changed correspondingly.