I store my artwork in the default locations that MePoTools artwork downloader saves them too. I chose to stick with those locations to make it easier for everyone.Everthing is fine.
Where do you store your artwork?
Becouse those directories should be the fefault Locations of MePo.
#StreamedMP.ArtistPath\..\..\CDArt\Music\ for example
refer to C:\ProgramData\Team MediaPortal\MediaPortal\Thumbs\CDArt\Music
Mediaportal alone doesn't (at last check) have any default locations for extra artwork such as cdart, clearart etc. The locations that the artwork is saved in are created by whichever plugin or application you use to download your artwork.