When I try to view artists in the now playing mode, it gives me weird blurred images
If you want to see local images instead, save custom images for artists in the parent folder of the thumb folder.
The (square) images in the thumb folder are used for thumbnail browser and artist view, and artist slide show uses its parent folder.
And open customize panel dialog for the artist picture view in now playing node> Untick retrieve web pictures option.
That setting also applies to theater mode and artist picture panel.