Album art limitations?

[ddeconin]

I have a folder.jpg in each folder that contains a ripped CD and I have cover art in each file.

From  http://wdc.custhelp.com/app/answers/detail/a_id/2742/~/how-to-show-thumbnails-on-a-wd-tv-(all-models)

I conclude I should cover art eveywhere , but that does not seem to be the case.