We updated our GitLab server from 9.0 to 9.3, and the GitLab Logo Plugin is no longer working correctly. The image tags are there but they're pointing to 404 locations, thereby making this plugin useless.
In one example, the img src is
but the correct name is now, apparently,
Notice the addition of "system" in the path)
Since we went from GitLab 9.0 to 9.3, I don't know in which release of GitLab this path changed, for sure.