I thought this might be the NT description field under SMB, but I changed that, and even rebooted the OMV server after changing that, and it doesn't seem to be changing the network name.
Instead, when from a Windows computer I browse to Network Places/Neighborhood, I'm just seeing my OMV server come up under the name "OPENMEDIAVAULT".
When I try to ping from the Windows computer, pinging OPENMEDIAVAULT works, whereas pinging the name I entered returns "could not find host".