Metadata and Artwork is generally stored on the server side. DLNA is just a format that standardizes the ability to stream media between different devices. Sounds like there is a misunderstanding about Server/Client relationship. I don't want to push you away from Mezzmo but if you aren't prepared to run a more feature rich server then you may want to scrap DLNA, try sideloading Kodi onto your FireTV and then build your library via network shares. The client is just seeing the media files and probably just displaying the titles as they are saved on the HDD. It sounds like you have a simple DLNA server on your router that can serve up media files but I would be really surprised if there were any way to configure your library to display artwork with any client, Mezzmo or not. In fact, I have never run into a setup that wasn't that way (Plex, Emby, Tversity, PS3 Media Server, etc.). My hard drive is plugged into my network router!Sounds like there is a misunderstanding about Server/Client relationship. It’s installed direct on the firetv ( I think android based )

Firetv upnp player