SongKong can find artwork from a number of sources and there are additional options available in the Artwork tab that let you refine how artwork is matched. But artwork quality can be a subjective notion, SongKong only replaces existing artwork with higher resolution artwork, but higher resolution is not always higher quality. Or you may already have artwork provided in a non-standard location such as iTunes artwork stored in your iTunes database and do not require it to be stored directly in your songs. For these reasons you might prefer SongKong to leave your artwork as it is, if so disable this option.