We have been running Zimbra with custom logos for our Network Edition Install (8.0.4 GA 5740) and just recently they have reverted back to the default "Zimbra" for the mail window and nothing for the login page. The domain configuration is still set with the custom logo URLs and they are accessible both internally and externally. I've given Zimbra a restart to see if that has helped and had no change. I can view the files on my Zimbra server just fine.
Interestingly if I try to set the theme to a new URL via the Global Settings the settings show as if they saved but re-visiting the page shows the blank values. I've flushed the theme cache and still no luck. I'm wondering if there is another spot or a log file to check as to why these would not display.