It's my understanding that Twonky is a media server that will install on Linux NAS and Linux x86 PC's in addition to Windows. (Unfortunately its not free you have to pay a small fee)
www.twonkyvision.de

I use Twonky occasionally via my XP PC as it serves my mp3 embedded Album Art to Media Streamer when playing audio tracks. I use Media Streamer to either play tracks directly on my Internet Tablet or control playback via my Philips Sl300i UPnP device connected to my Hi-Fi. (TVersity Release 0.9.10.7 is currently unable to serve the Album Art)