obtain the cover art by using a program that supports tagging such as mp3tag, tagscanner, winamp etc. (they all work with FLAC not just MP3) - tagscanner makes finding cover art easier but i prefer mp3tag for overall ease of use. Winamp is a great media player but it uses the gracenote db which is not too hot for cover art especially for older or less popular titles, besides, winamp does not embed the artwork in the file it uses folder.jpg (or a file of your choice). You could also use Windows Media Player but I don’t like the way it spreads hidden jpeg files all over the relevant folder. The metadata does not seem very accurate either.
use “manual” artwork ie. if you have a media file called rumours.flac then the artwork file should be called rumours.jpg etc.
There’s no cover art on the CD if that’s what you are thinking.
You have to obtain the cover art from the internet, then either a) embed it in the FLAC file [the cover is another tag, just like the title, artist etc.] or b) use the WDTV manual method as I described in (2) above. I would recommend the 1st method because a) less files=less mess in the directory b) the jpegs will not show up under the WDTV ‘Photos’ menu and c) it’s just less work when dealing with many files
EDIT: BTW, the ideal cover art size is 300x300, because that’s the size of the graphic you see when the song is playing.