dBpoweramp's CD Ripper does add cover art automatically. You can quickly check for other versions of the cover art as well. It's what I use to rip CDs to FLAC.
I use dbripper and it does automaticaly pull in art. It even gives you choices of various versions of the same cd. But I also have lots of obscure classical recordings where there is no album art on line. So I just scan the CD cover and paste into the file while in JRiver.
I am about to purchase a ripper/streamer like Innuous but am concerned about whether I can edit the metadata as I can with JRiver?
Did you campare the Lumin to the Innuose?