It means it's not supported. There are far too many discussions about the issue you are writing about and there appears to be no solid answer for some of us. I know it's something amiss with the encoding support. BUT these devices have very limited encoding and shoving content over AllShare reduces that even further.
I'd look at replacements for AllShare if you don't want to twiddle, fiddle and play with encoding and file names.
Samsung BlueRay Player BD-E5700 - Firmware 2012/03/22_001009
Installed on PC - AllShare version 126.96.36.19913_8
When playing music through AllShare on the BD-E5700 from files on my computer on the left of the TV screen while playing music it does not display the artist name or front cover tag art. It just shows "Unknown" for the artist and shows tag art as a graphic of two music notes. It does display the song title, album name and genre. But not the artist!
When browsing through folders on the TV screen the front cover tag are shows correctly. But as soon as you select a file to play and the Music play screen appears the front cover tag art does not show and the artist name is displayed as "Unknown".
My music library is composed entirely of MP3 files all of which have 200X200 pixel ID3v2.x front cover tag art in the files and they display correctly on all my other devises.