You can use either WMP10, WMP11 or the Emodio v.1.0. There could be several reasons that some album art isn't shown - it may not have been downloaded prior to the rip, or it may not have been properly attached to the file. While you might be able to launch the file on the computer, Windows Media Player may search and find the album art, but it doesn't necessarily mean that it is embedded.
One other option is to find a small picture of the album art you want, and then add that in the album folder. In some cases, that may help solve the issue as well.
Dear Mr Samsung Tech: what program does Samsung recommend using to rip Cd's to the P3 media player, Emodio or WMP 11 ? Also, would you happen to know why the album art doesn't transfer to the P3 using either of these programs. The version Emodio is 220.127.116.11. Thank you.